diff --git a/app/graphql/types/exam_version_type.rb b/app/graphql/types/exam_version_type.rb
index 36d562f93..0d1864e79 100644
--- a/app/graphql/types/exam_version_type.rb
+++ b/app/graphql/types/exam_version_type.rb
@@ -123,7 +123,7 @@ def instructions
       guard ALL_STAFF_OR_PUBLISHED
     end
 
-    field :all_rubrics, [Types::RubricType], null: true do
+    field :all_rubrics, [Types::RubricType], null: false do
       guard Guards::ALL_STAFF
     end
     def all_rubrics
@@ -132,7 +132,7 @@ def all_rubrics
         .load(object)
     end
 
-    field :rubrics, [Types::RubricType], null: true do
+    field :rubrics, [Types::RubricType], null: false do
       guard Guards::ALL_STAFF
     end
     def rubrics
@@ -141,11 +141,11 @@ def rubrics
         .load(object)
     end
 
-    field :root_rubric, Types::RubricType, null: true do
+    field :root_rubric, Types::RubricType, null: false do
       guard Guards::ALL_STAFF
     end
 
-    field :raw_rubrics, GraphQL::Types::JSON, null: true do
+    field :raw_rubrics, GraphQL::Types::JSON, null: false do
       guard Guards::PROFESSORS
     end
     def raw_rubrics
diff --git a/app/graphql/types/grading_comment_type.rb b/app/graphql/types/grading_comment_type.rb
index fae614cae..5d90c23f5 100644
--- a/app/graphql/types/grading_comment_type.rb
+++ b/app/graphql/types/grading_comment_type.rb
@@ -26,6 +26,5 @@ def bnum
     field :message, String, null: false
     field :points, Float, null: false
     field :creator, Types::UserType, null: false
-    field :preset_comment, Types::PresetCommentType, null: true
   end
 end
diff --git a/app/javascript/components/common/NumericInput.tsx b/app/javascript/components/common/NumericInput.tsx
index 1f429b57f..8a3776a54 100644
--- a/app/javascript/components/common/NumericInput.tsx
+++ b/app/javascript/components/common/NumericInput.tsx
@@ -69,7 +69,9 @@ const validateNumericInput : KeyboardEventHandler<HTMLInputElement> = (e) => {
   if (e.key === '.') {
     const indexOfDot = e.currentTarget.value.indexOf('.');
     if (indexOfDot < 0) return;
-    if (e.currentTarget.selectionStart <= indexOfDot
+    if (e.currentTarget.selectionStart !== null
+        && e.currentTarget.selectionStart <= indexOfDot
+        && e.currentTarget.selectionEnd !== null
         && indexOfDot < e.currentTarget.selectionEnd) {
       return;
     }
@@ -77,7 +79,9 @@ const validateNumericInput : KeyboardEventHandler<HTMLInputElement> = (e) => {
   if (e.key === '-') {
     const indexOfMinus = e.currentTarget.value.indexOf('-');
     if (indexOfMinus < 0 && e.currentTarget.selectionStart === 0) return;
-    if (e.currentTarget.selectionStart <= indexOfMinus
+    if (e.currentTarget.selectionStart !== null
+        && e.currentTarget.selectionStart <= indexOfMinus
+        && e.currentTarget.selectionEnd !== null
         && indexOfMinus < e.currentTarget.selectionEnd) {
       return;
     }
@@ -147,7 +151,7 @@ export const NumericInput: React.FC<{
           const selEnd = e.currentTarget.selectionEnd;
           const nextVal = `${curVal.slice(0, selStart)}${data}${curVal.slice(selEnd)}`;
           const nextAsNum = Number(nextVal);
-          if (Number.isFinite(nextAsNum)) {
+          if (Number.isFinite(nextAsNum) && onChange) {
             onChange(clamp(nextAsNum, min, max), true);
           }
         }}
@@ -167,7 +171,7 @@ export const NumericInput: React.FC<{
             variant={variant}
             disabled={disabled || (max !== undefined && numValue >= max)}
             tabIndex={-1}
-            onClick={() => onChange(clamp(numValue + step, min, max), false)}
+            onClick={() => onChange && onChange(clamp(numValue + step, min, max), false)}
           >
             <Icon className="m-0 p-0" size={size === 'lg' ? '0.75em' : '0.5em'} I={FaChevronUp} />
           </Button>
@@ -177,7 +181,7 @@ export const NumericInput: React.FC<{
             variant={variant}
             disabled={disabled || (min !== undefined && numValue <= min)}
             tabIndex={-1}
-            onClick={() => onChange(clamp(numValue - step, min, max), false)}
+            onClick={() => onChange && onChange(clamp(numValue - step, min, max), false)}
           >
             <Icon size={size === 'lg' ? '0.75em' : '0.5em'} I={FaChevronDown} />
           </Button>
diff --git a/app/javascript/components/common/ReadableDate.tsx b/app/javascript/components/common/ReadableDate.tsx
index adc38bbe0..22f9c0182 100644
--- a/app/javascript/components/common/ReadableDate.tsx
+++ b/app/javascript/components/common/ReadableDate.tsx
@@ -1,12 +1,12 @@
 import React from 'react';
-import { DateTime, Duration } from 'luxon';
+import { DateTime } from 'luxon';
 
 function makeReadableDate(dd: DateTime, showTime: boolean, capitalize: boolean): string {
   const today = DateTime.local().startOf('day');
   const yesterday = today.minus({ days: 1 });
   const tomorrow = today.plus({ days: 1 });
   const twodays = tomorrow.plus({ days: 1 });
-  let relDay: string;
+  let relDay: string | undefined;
   if (yesterday <= dd && dd < today) {
     relDay = (capitalize ? 'Yesterday' : 'yesterday');
   } else if (today <= dd && dd < tomorrow) {
@@ -28,7 +28,6 @@ interface ReadableDateProps {
   value: DateTime;
   relative?: boolean;
   showTime?: boolean;
-  threshold?: Duration;
   capitalize?: boolean;
 }
 
@@ -40,11 +39,11 @@ const ReadableDate: React.FC<ReadableDateProps> = (props) => {
     className,
     capitalize,
   } = props;
-  let str: string;
+  let str: string | null;
   if (relative) {
     str = value.toRelative();
   } else {
-    str = makeReadableDate(value, showTime, capitalize);
+    str = makeReadableDate(value, showTime, !!capitalize);
   }
   return (
     <span className={className}>{str}</span>
diff --git a/app/javascript/components/common/alerts.tsx b/app/javascript/components/common/alerts.tsx
index 26e2cdfd0..cd6afd6b8 100644
--- a/app/javascript/components/common/alerts.tsx
+++ b/app/javascript/components/common/alerts.tsx
@@ -38,7 +38,7 @@ const ShowAlert: React.FC<{
     copyButton = false,
   } = alert;
   const [show, setShow] = useState(true);
-  const bodyRef = useRef<HTMLDivElement>();
+  const bodyRef = useRef<HTMLDivElement>(null);
   return (
     <Toast
       className={`border-${variant}`}
@@ -55,8 +55,10 @@ const ShowAlert: React.FC<{
             className="p-0"
             variant={variant}
             onClick={async () => {
-              const text = bodyRef.current.innerText;
-              await navigator.clipboard.writeText(text);
+              if (bodyRef.current) {
+                const text = bodyRef.current.innerText;
+                await navigator.clipboard.writeText(text);
+              }
             }}
           >
             <Icon I={FaCopy} />
diff --git a/app/javascript/components/common/archive/fileMarks.ts b/app/javascript/components/common/archive/fileMarks.ts
index f3dd88a73..ca57c2c66 100644
--- a/app/javascript/components/common/archive/fileMarks.ts
+++ b/app/javascript/components/common/archive/fileMarks.ts
@@ -1,5 +1,8 @@
 interface MarksInfo {
-  byLine: unknown[];
+  byLine: {
+    open: number[],
+    close: number[],
+  }[][];
   byNum: {
     [num: number]: {
       startLine: number;
@@ -37,7 +40,7 @@ export function extractMarks(text: string): FileMarksInfo {
     let idx: number;
     // eslint-disable-next-line no-cond-assign
     while ((idx = lines[lineNo].search(/~ro:\d+:[se]~/)) >= 0) {
-      const m = lines[lineNo].match(/~ro:(\d+):([se])~/);
+      const m = lines[lineNo].match(/~ro:(\d+):([se])~/) as RegExpMatchArray;
       lines[lineNo] = lines[lineNo].replace(m[0], '');
       if (m[2] === 's') {
         count += 1;
@@ -81,7 +84,7 @@ export function extractMarks(text: string): FileMarksInfo {
       },
       options: {
         inclusiveLeft: m.lockBefore,
-        inclusiveRight: m.lockAfter,
+        inclusiveRight: !!m.lockAfter,
       },
     })),
   };
diff --git a/app/javascript/components/common/archive/index.tsx b/app/javascript/components/common/archive/index.tsx
index 756b26e35..5926dde31 100644
--- a/app/javascript/components/common/archive/index.tsx
+++ b/app/javascript/components/common/archive/index.tsx
@@ -4,17 +4,19 @@ import mime from '@hourglass/common/mime';
 import { extractMarks } from '@hourglass/common/archive/fileMarks';
 
 export async function handleDir(root: JSZip): Promise<ExamFile[]> {
-  const ret = [];
-  const promises = [];
+  const ret: ExamFile[] = [];
+  const promises: Promise<void>[] = [];
   root.forEach((path, file) => {
     if (file.dir) return;
     const exploded = path.split('/');
-    const fileName = exploded.pop();
-    let current = ret;
-    const pathSoFar = [];
+    // since the split condition is non-empty, the exploded array will be non-empty
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const fileName = exploded.pop()!;
+    let current: ExamFile[] = ret;
+    const pathSoFar: string[] = [];
     exploded.forEach((segment) => {
       pathSoFar.push(segment);
-      const dir = current.find((f) => f.text === `${segment}/`);
+      const dir = current.find((f): f is ExamDir => f.text === `${segment}/`);
       if (dir) {
         current = dir.nodes;
       } else {
diff --git a/app/javascript/components/common/helpers.ts b/app/javascript/components/common/helpers.ts
index fd876de86..81e591f6c 100644
--- a/app/javascript/components/common/helpers.ts
+++ b/app/javascript/components/common/helpers.ts
@@ -65,3 +65,7 @@ export type SelectOptions<T> = SelectOption<T>[];
 export type MutationReturn<T extends MutationParameters> = [
   MutateWithVariables<T>, MutationState<T>
 ];
+
+export function compact<T>(ts : readonly (T | null | undefined)[]): T[] {
+  return ts.filter((t : T | null | undefined): t is T => t !== null && t !== undefined);
+}
diff --git a/app/javascript/components/common/student-dnd/index.tsx b/app/javascript/components/common/student-dnd/index.tsx
index 912240041..e22d1c56d 100644
--- a/app/javascript/components/common/student-dnd/index.tsx
+++ b/app/javascript/components/common/student-dnd/index.tsx
@@ -36,7 +36,7 @@ interface Section {
 
 interface Student {
   id: string;
-  nuid: number;
+  nuid: number | null;
   username: string;
   displayName: string;
 }
@@ -329,7 +329,7 @@ const StudentDNDForm: React.FC<
             <Button
               disabled={loading}
               variant="danger"
-              className={pristine && 'd-none'}
+              className={pristine ? 'd-none' : undefined}
               onClick={reset}
             >
               Reset
diff --git a/app/javascript/components/common/types/api.ts b/app/javascript/components/common/types/api.ts
index bdd4cc7c2..33ea251bc 100644
--- a/app/javascript/components/common/types/api.ts
+++ b/app/javascript/components/common/types/api.ts
@@ -76,8 +76,8 @@ export function useApiResponse<Server, Res = Server>(
   transformSuccess?: (server: Server) => Res,
   deps?: React.DependencyList,
 ): ApiResponse<Res> {
-  const [response, setResponse] = useState<Server>(undefined);
-  const [error, setError] = useState<ApiError>(undefined);
+  const [response, setResponse] = useState<Server | undefined>(undefined);
+  const [error, setError] = useState<ApiError | undefined>(undefined);
   useEffect(() => {
     fetch(url, {
       headers: {
diff --git a/app/javascript/components/workflows/grading/UseRubrics.tsx b/app/javascript/components/workflows/grading/UseRubrics.tsx
index dccc538e4..1c5bd8276 100644
--- a/app/javascript/components/workflows/grading/UseRubrics.tsx
+++ b/app/javascript/components/workflows/grading/UseRubrics.tsx
@@ -1,4 +1,4 @@
-import React, { useContext } from 'react';
+import React, { ReactElement, useContext } from 'react';
 import {
   Rubric,
   RubricOne,
@@ -39,13 +39,19 @@ import { createCommentMutation } from './__generated__/createCommentMutation.gra
 import { grading_one$data } from './__generated__/grading_one.graphql';
 import { UseRubricsKey$key } from './__generated__/UseRubricsKey.graphql';
 
-type GradingComment = grading_one$data['gradingComments']['edges'][number]['node'];
-type PresetCommentId = GradingComment['presetComment']['id']
+type NN<T> = Exclude<T, null>
+type O<T> = T | undefined
+
+type GradingComment = NN<NN<NN<NN<grading_one$data['gradingComments']>['edges']>[number]>['node']>;
+type PresetCommentId = NN<GradingComment['presetComment']>['id']
 
 interface ShowRubricProps<R> {
   rubric: R;
+  // eslint-disable-next-line react/no-unused-prop-types
   showCompletenessAgainst?: PresetCommentId[];
+  // eslint-disable-next-line react/no-unused-prop-types
   parentRubricType?: Rubric['type'];
+  // eslint-disable-next-line react/no-unused-prop-types
   collapseKey?: string;
   qnum: number;
   pnum: number;
@@ -127,7 +133,7 @@ const ShowPreset: React.FC<{
 };
 
 type CompletionStatus = 'complete' | 'incomplete' | 'invalid'
-function combineCompletionAll(c1 : CompletionStatus, c2: CompletionStatus): CompletionStatus {
+function combineCompletionAll(c1 : CompletionStatus, c2: O<CompletionStatus>): O<CompletionStatus> {
   // complete < incomplete < invalid
   switch (c1) {
     case 'complete': return c2;
@@ -137,7 +143,7 @@ function combineCompletionAll(c1 : CompletionStatus, c2: CompletionStatus): Comp
       throw new ExhaustiveSwitchError(c1);
   }
 }
-function combineCompletionAny(c1 : CompletionStatus, c2: CompletionStatus): CompletionStatus {
+function combineCompletionAny(c1: CompletionStatus, c2: O<CompletionStatus>): O<CompletionStatus> {
   // incomplete < complete < invalid
   switch (c1) {
     case 'incomplete': return c2;
@@ -147,7 +153,7 @@ function combineCompletionAny(c1 : CompletionStatus, c2: CompletionStatus): Comp
       throw new ExhaustiveSwitchError(c1);
   }
 }
-function completionStatus(rubric: Rubric, parentRubricType: Rubric['type'], presetIDs: PresetCommentId[]): CompletionStatus {
+function completionStatus(rubric: Rubric, parentRubricType: O<Rubric['type']>, presetIDs: O<PresetCommentId[]>): O<CompletionStatus> {
   if (rubric === undefined || rubric === null) return undefined;
   if (presetIDs === undefined || presetIDs === null) return undefined;
   switch (rubric.type) {
@@ -198,7 +204,7 @@ function completionStatus(rubric: Rubric, parentRubricType: Rubric['type'], pres
       throw new ExhaustiveSwitchError(rubric);
   }
 }
-const statusToClass = (status: CompletionStatus): string => {
+const statusToClass = (status: O<CompletionStatus>): string => {
   if (status === 'complete') {
     return 'status-valid';
   }
@@ -210,8 +216,8 @@ const statusToClass = (status: CompletionStatus): string => {
 
 export const ShowPresetSummary: React.FC<{
   direction: RubricPresets['direction'];
-  label: string;
-  mercy: number;
+  label?: string;
+  mercy?: number;
   pointsMsg?: string;
 }> = (props) => {
   const {
@@ -357,7 +363,7 @@ const ShowAll: React.FC<ShowRubricProps<RubricAll>> = (props) => {
   }
   const showAnyway = (collapseKey === undefined ? 'show' : '');
   const padDescription = (description ? 'mb-2' : '');
-  let chevron = null;
+  let chevron: O<ReactElement>;
   if (showChevron) {
     if (isOpen) {
       chevron = <Icon className="mr-2" I={FaChevronUp} />;
@@ -379,11 +385,11 @@ const ShowAll: React.FC<ShowRubricProps<RubricAll>> = (props) => {
   );
   return (
     <>
-      <Accordion.Toggle as={Card.Header} eventKey={collapseKey}>
+      <Accordion.Toggle as={Card.Header} eventKey={collapseKey as string}>
         {heading}
         <HTML value={description} className={padDescription} />
       </Accordion.Toggle>
-      <Accordion.Collapse className={showAnyway} eventKey={collapseKey}>
+      <Accordion.Collapse className={showAnyway} eventKey={collapseKey as string}>
         <Card.Body>
           {body}
         </Card.Body>
@@ -450,7 +456,7 @@ const ShowOne: React.FC<ShowRubricProps<RubricOne>> = (props) => {
   }
   const showAnyway = (showChevron ? '' : 'show');
   const padDescription = (description ? 'mb-2' : '');
-  let chevron = null;
+  let chevron: O<ReactElement>;
   if (showChevron) {
     if (isOpen) {
       chevron = <Icon className="mr-2" I={FaChevronUp} />;
@@ -472,11 +478,11 @@ const ShowOne: React.FC<ShowRubricProps<RubricOne>> = (props) => {
   );
   return (
     <>
-      <Accordion.Toggle as={Card.Header} eventKey={collapseKey}>
+      <Accordion.Toggle as={Card.Header} eventKey={collapseKey as string}>
         {heading}
         <HTML value={description} className={padDescription} />
       </Accordion.Toggle>
-      <Accordion.Collapse className={showAnyway} eventKey={collapseKey}>
+      <Accordion.Collapse className={showAnyway} eventKey={collapseKey as string}>
         <Card.Body>
           {body}
         </Card.Body>
@@ -543,7 +549,7 @@ const ShowAny: React.FC<ShowRubricProps<RubricAny>> = (props) => {
   }
   const showAnyway = (showChevron ? '' : 'show');
   const padDescription = (description ? 'mb-2' : '');
-  let chevron = null;
+  let chevron: O<ReactElement>;
   if (showChevron) {
     if (isOpen) {
       chevron = <Icon className="mr-2" I={FaChevronUp} />;
@@ -565,11 +571,11 @@ const ShowAny: React.FC<ShowRubricProps<RubricAny>> = (props) => {
   );
   return (
     <>
-      <Accordion.Toggle as={Card.Header} eventKey={collapseKey}>
+      <Accordion.Toggle as={Card.Header} eventKey={collapseKey as string}>
         {heading}
         <HTML value={description} className={padDescription} />
       </Accordion.Toggle>
-      <Accordion.Collapse className={showAnyway} eventKey={collapseKey}>
+      <Accordion.Collapse className={showAnyway} eventKey={collapseKey as string}>
         <Card.Body>
           {body}
         </Card.Body>
diff --git a/app/javascript/components/workflows/grading/index.tsx b/app/javascript/components/workflows/grading/index.tsx
index 737d00331..712aa7c97 100644
--- a/app/javascript/components/workflows/grading/index.tsx
+++ b/app/javascript/components/workflows/grading/index.tsx
@@ -63,6 +63,7 @@ import {
   alphabetIdx,
   useRefresher,
   pluralize,
+  compact,
 } from '@hourglass/common/helpers';
 import DisplayAllThatApply from '@proctor/registrations/show/questions/DisplayAllThatApply';
 import DisplayMultipleChoice from '@proctor/registrations/show/questions/DisplayMultipleChoice';
@@ -190,7 +191,7 @@ const ShowStatusIcon: React.FC<{
   );
 };
 
-function isNode(et: EventTarget): et is Node {
+function isNode(et: EventTarget | null): et is Node {
   return et instanceof Node;
 }
 
@@ -225,9 +226,9 @@ const Feedback: React.FC<{
   useEffect(() => {
     setPointStr(String(points));
   }, [points]);
-  const alertRef = useRef<HTMLDivElement>();
+  const alertRef = useRef<HTMLDivElement>(null);
   useLayoutEffect(() => {
-    if (isFocused) { alertRef.current.focus(); }
+    if (isFocused) { alertRef.current?.focus(); }
   }, [isFocused]);
   const variant = variantForPoints(points);
   const VariantIcon = iconForPoints(points);
@@ -241,7 +242,7 @@ const Feedback: React.FC<{
           if (onBlur) onBlur(e);
           return; // don't setFocused and collapse this editor yet.
         }
-        if (isNode(e.relatedTarget) && alertRef.current.contains(e.relatedTarget)) return;
+        if (isNode(e.relatedTarget) && alertRef.current?.contains(e.relatedTarget)) return;
         if (onBlur) onBlur(e);
         setFocused(false);
       }}
@@ -339,7 +340,7 @@ const Feedback: React.FC<{
 };
 
 const PromptRow: React.FC<{
-  prompt: HTMLVal;
+  prompt?: HTMLVal;
 }> = ({ prompt }) => (
   <Row>
     <Col sm={{ span: 6, offset: 3 }}>
@@ -505,7 +506,10 @@ const NewComments: React.FC<{
   );
 };
 
-type GradingComment = grading_one$data['gradingComments']['edges'][number]['node'];
+type NN<T> = Exclude<T, null>
+type O<T> = T | undefined
+
+type GradingComment = NN<NN<NN<NN<grading_one$data['gradingComments']>['edges']>[number]>['node']>;
 
 const DESTROY_COMMENT_MUTATION = graphql`
   mutation gradingDestroyCommentMutation($input: DestroyGradingCommentInput!) {
@@ -547,7 +551,7 @@ const SavedComment: React.FC<{
     presetComment,
   } = comment;
   const { alert } = useContext(AlertContext);
-  const [error, setError] = useState<string>(null);
+  const [error, setError] = useState<string | null>(null);
   const [value, setValue] = useState<CommentVal>({
     message,
     points,
@@ -568,12 +572,14 @@ const SavedComment: React.FC<{
     }));
   };
   const onReset = () => {
-    setStatus(CommentSaveStatus.DIRTY);
-    setValue((old) => ({
-      ...old,
-      message: presetComment.studentFeedback ?? presetComment.graderHint,
-      points: presetComment.points,
-    }));
+    if (presetComment) {
+      setStatus(CommentSaveStatus.DIRTY);
+      setValue((old) => ({
+        ...old,
+        message: presetComment.studentFeedback ?? presetComment.graderHint,
+        points: presetComment.points,
+      }));
+    }
   };
   const couldReset = (presetComment instanceof Object)
     && ((value.message !== presetComment.studentFeedback
@@ -652,7 +658,7 @@ const SavedComment: React.FC<{
       status={status}
       onRemove={removeComment}
       onBlur={doUpdate}
-      error={error}
+      error={error ?? undefined}
     />
   );
 };
@@ -712,13 +718,13 @@ interface AnswersRowProps<T, V> {
   ShowStudent?: React.ComponentType<{
     info: T,
     value: V,
-    refreshProps: React.DependencyList;
+    refreshProps?: React.DependencyList;
     fullyExpandCode?: boolean;
   }>;
   ShowExpected: React.ComponentType<{
     info: T,
     value: V,
-    refreshProps: React.DependencyList;
+    refreshProps?: React.DependencyList;
     fullyExpandCode?: boolean;
   }>;
   info: T;
@@ -730,7 +736,7 @@ interface AnswersRowProps<T, V> {
   bnum: number;
   comments: GradingComment[];
   registrationId: string;
-  refreshProps: React.DependencyList;
+  refreshProps?: React.DependencyList;
 }
 
 function AnswersRow<T, V>(
@@ -830,7 +836,7 @@ function AnswersRow<T, V>(
               qnumRubricKey={qnumRubricKey}
               pnumRubricKey={pnumRubricKey}
               bnumRubricKey={bnumRubricKey}
-              showCompletenessAgainst={comments.map((c) => c.presetComment?.id)}
+              showCompletenessAgainst={compact(comments.map((c) => c.presetComment?.id))}
               registrationId={registrationId}
               qnum={qnum}
               pnum={pnum}
@@ -844,14 +850,15 @@ function AnswersRow<T, V>(
 }
 
 const GradeBodyItem: React.FC<{
-  expectedAnswer: AnswerState;
-  studentAnswer: AnswerState;
+  expectedAnswer?: AnswerState;
+  studentAnswer?: AnswerState;
   info: BodyItemInfo;
   qnum: number;
   pnum: number;
   bnum: number;
   examVersionKey: gradingRubric$key;
-  check?: grading_one$data['gradingChecks'][number];
+  // eslint-disable-next-line react/no-unused-prop-types
+  check?: NN<grading_one$data['gradingChecks']>[number];
   comments: GradingComment[];
   registrationId: string;
   refreshProps: React.DependencyList;
@@ -884,8 +891,8 @@ const GradeBodyItem: React.FC<{
             bnum={bnum}
             info={info}
             ShowExpected={DisplayCode}
-            studentAnswer={studentAnswer as CodeState}
-            expectedAnswer={expectedAnswer as CodeState}
+            studentAnswer={studentAnswer as O<CodeState>}
+            expectedAnswer={expectedAnswer as O<CodeState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -903,8 +910,8 @@ const GradeBodyItem: React.FC<{
             bnum={bnum}
             info={info}
             ShowExpected={DisplayCodeTag}
-            studentAnswer={studentAnswer as CodeTagState}
-            expectedAnswer={expectedAnswer as CodeTagState}
+            studentAnswer={studentAnswer as O<CodeTagState>}
+            expectedAnswer={expectedAnswer as O<CodeTagState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -923,8 +930,8 @@ const GradeBodyItem: React.FC<{
             info={info}
             ShowStudent={GradeYesNo}
             ShowExpected={DisplayYesNo}
-            studentAnswer={studentAnswer as YesNoState}
-            expectedAnswer={expectedAnswer as YesNoState}
+            studentAnswer={studentAnswer as O<YesNoState>}
+            expectedAnswer={expectedAnswer as O<YesNoState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -942,8 +949,8 @@ const GradeBodyItem: React.FC<{
             bnum={bnum}
             info={info}
             ShowExpected={DisplayText}
-            studentAnswer={studentAnswer as TextState}
-            expectedAnswer={expectedAnswer as TextState}
+            studentAnswer={studentAnswer as O<TextState>}
+            expectedAnswer={expectedAnswer as O<TextState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -962,8 +969,8 @@ const GradeBodyItem: React.FC<{
             info={info}
             ShowStudent={GradeMatching}
             ShowExpected={DisplayMatching}
-            studentAnswer={studentAnswer as MatchingState}
-            expectedAnswer={expectedAnswer as MatchingState}
+            studentAnswer={studentAnswer as O<MatchingState>}
+            expectedAnswer={expectedAnswer as O<MatchingState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -981,8 +988,8 @@ const GradeBodyItem: React.FC<{
             bnum={bnum}
             info={info}
             ShowExpected={DisplayAllThatApply}
-            studentAnswer={studentAnswer as AllThatApplyState}
-            expectedAnswer={expectedAnswer as AllThatApplyState}
+            studentAnswer={studentAnswer as O<AllThatApplyState>}
+            expectedAnswer={expectedAnswer as O<AllThatApplyState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -1001,8 +1008,8 @@ const GradeBodyItem: React.FC<{
             info={info}
             ShowStudent={GradeMultipleChoice}
             ShowExpected={DisplayMultipleChoice}
-            studentAnswer={studentAnswer as MultipleChoiceState}
-            expectedAnswer={expectedAnswer as MultipleChoiceState}
+            studentAnswer={studentAnswer as O<MultipleChoiceState>}
+            expectedAnswer={expectedAnswer as O<MultipleChoiceState>}
             comments={comments}
             registrationId={registrationId}
             refreshProps={refreshProps}
@@ -1139,7 +1146,8 @@ const Grade: React.FC<{
   const { examId, registrationId } = useParams<{ examId: string; registrationId: string }>();
   const { examVersion } = res;
   const currentAnswers = res.currentAnswers as AnswersState;
-  const { answers, dbQuestions } = examVersion;
+  const { dbQuestions } = examVersion;
+  const answers = examVersion.answers as AnswerState[][][];
   const files = examVersion.files as ExamFile[];
   const contextVal = useMemo(() => ({
     files,
@@ -1156,7 +1164,8 @@ const Grade: React.FC<{
           registrationId: nextRegId,
           qnum: nextQ,
           pnum: nextP,
-        } = gradeNext;
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        } = gradeNext!;
         history.replace(`/exams/${examId}/grading/${nextRegId}/${nextQ}/${nextP}`);
       },
       onError: () => {
@@ -1214,7 +1223,7 @@ const Grade: React.FC<{
   const nextExamLoading = releaseNextLoading || releaseFinishLoading || nextLoading;
   const singlePart = dbQuestions[qnum].parts.length === 1
     && !dbQuestions[qnum].parts[0].name?.value?.trim();
-  const allComments = res.gradingComments.edges.map(({ node }) => node);
+  const allComments = compact(res.gradingComments?.edges?.map((e) => e?.node) ?? []);
   const anyUncommentedItems = dbQuestions[qnum].parts[pnum].bodyItems.some((b, bnum) => (
     ((b.info as BodyItemInfo).type !== 'HTML')
       && (allComments.filter((c) => (c.qnum === qnum && c.pnum === pnum && c.bnum === bnum))
@@ -1227,12 +1236,12 @@ const Grade: React.FC<{
           <Row>
             <Col sm={{ span: 6, offset: 3 }}>
               <h2>
-                <QuestionName qnum={qnum} name={dbQuestions[qnum].name} />
+                <QuestionName qnum={qnum} name={dbQuestions[qnum].name ?? undefined} />
                 {dbQuestions[qnum].extraCredit ? <span className="ml-4">(Extra credit)</span> : null}
               </h2>
             </Col>
           </Row>
-          <PromptRow prompt={dbQuestions[qnum].description} />
+          <PromptRow prompt={dbQuestions[qnum].description ?? undefined} />
           {dbQuestions[qnum].references.length !== 0 && (
             <Row>
               <Col sm={{ span: 9, offset: 3 }}>
@@ -1250,12 +1259,12 @@ const Grade: React.FC<{
                   <PartName
                     anonymous={singlePart}
                     pnum={pnum}
-                    name={dbQuestions[qnum].parts[pnum].name}
+                    name={dbQuestions[qnum].parts[pnum].name ?? undefined}
                   />
                 </h3>
               </Col>
             </Row>
-            <PromptRow prompt={dbQuestions[qnum].parts[pnum].description} />
+            <PromptRow prompt={dbQuestions[qnum].parts[pnum].description ?? undefined} />
             {dbQuestions[qnum].parts[pnum].references.length !== 0 && (
               <Row>
                 <Col sm={{ span: 9, offset: 3 }}>
@@ -1272,7 +1281,7 @@ const Grade: React.FC<{
 
               const ans = answers[qnum][pnum][bnum];
               const expectedAnswer = isNoAns(ans) ? undefined : ans;
-              const check = res.gradingChecks.find((c) => (
+              const check = res.gradingChecks?.find((c) => (
                 c.qnum === qnum
                 && c.pnum === pnum
                 && c.bnum === bnum
@@ -1479,10 +1488,10 @@ const ShowOnePart: React.FC<{
         <div>
           <Row>
             <Col sm={{ span: 6, offset: 3 }}>
-              <h2><QuestionName qnum={qnum} name={questions[qnum].name} /></h2>
+              <h2><QuestionName qnum={qnum} name={questions[qnum].name ?? undefined} /></h2>
             </Col>
           </Row>
-          <PromptRow prompt={questions[qnum].description} />
+          <PromptRow prompt={questions[qnum].description ?? undefined} />
           {questions[qnum].references.length !== 0 && (
             <Row>
               <Col sm={{ span: 9, offset: 3 }}>
@@ -1541,7 +1550,7 @@ const GradeOnePart: React.FC = () => {
   if (res.error) {
     return <Container><RenderError error={res.error} /></Container>;
   }
-  if (!res.data) {
+  if (!res.data || !res.data.registration) {
     return <Container><p>Loading...</p></Container>;
   }
   return <GradeOnePartHelp registration={res.data.registration} qnum={qnum} pnum={pnum} />;
@@ -1550,7 +1559,7 @@ const GradeOnePart: React.FC = () => {
 const GradeOnePartHelp: React.FC<{
   qnum: string,
   pnum: string,
-  registration: gradingQuery['response']['registration'],
+  registration: NN<gradingQuery['response']['registration']>,
 }> = (props) => {
   const { registration, qnum, pnum } = props;
   const { qpPairs } = registration.examVersion;
@@ -1626,11 +1635,20 @@ const SyncExamToBottlenoseButton: React.FC = () => {
     SYNC_EXAM_TO_BOTTLENOSE_MUTATION,
     {
       onCompleted: ({ syncExamToBottlenose }) => {
-        alert({
-          variant: 'success',
-          title: 'Exam synced',
-          message: `${syncExamToBottlenose.exam.name} was synced successfully.`,
-        });
+        if (syncExamToBottlenose) {
+          alert({
+            variant: 'success',
+            title: 'Exam synced',
+            message: `${syncExamToBottlenose.exam.name} was synced successfully.`,
+          });
+        } else {
+          alert({
+            variant: 'danger',
+            title: 'Error syncing exam',
+            message: 'No data received from server',
+            copyButton: true,
+          });
+        }
       },
       onError: (err) => {
         alert({
@@ -1669,14 +1687,16 @@ const allBlank = (stats) => {
   return stats.notStarted === 0;
 };
 
-type GradingLockInfo = gradingMyGrading['examVersions']['edges'][number]['node']['inProgress']['edges'][number]['node'];
-type QPInfo = gradingMyGrading['examVersions']['edges'][number]['node']['qpPairs'];
+type GradingLockInfo = NN<NN<NN<NN<NN<NN<gradingMyGrading['examVersions']['edges']>[number]>['node']>['inProgress']['edges']>[number]>['node']>;
+type QPInfo = NN<NN<NN<gradingMyGrading['examVersions']['edges']>[number]>['node']>['qpPairs'];
 
 const groupTree = (
-  collection: {readonly edges: readonly {readonly node: GradingLockInfo}[]},
+  collection: {
+    readonly edges: readonly ({readonly node: GradingLockInfo | null} | null)[] | null
+  } | null,
 ): GradingLockInfo[][][] => {
   const tree : GradingLockInfo[][][] = [];
-  collection.edges.forEach(({ node }) => {
+  compact(collection?.edges?.map((e) => e?.node) ?? []).forEach((node) => {
     const { qnum, pnum } = node;
     tree[qnum] = tree[qnum] ?? [];
     tree[qnum][pnum] = tree[qnum][pnum] ?? [];
@@ -1950,13 +1970,13 @@ const MyGrading: React.FC<{
   return (
     <div>
       <h3>My grading so far</h3>
-      {res.examVersions.edges.map(({ node }) => {
+      {compact(res.examVersions.edges?.map((e) => e?.node) ?? []).map((node) => {
         const inProgressTree = groupTree(node.inProgress);
         const finishedTree = groupTree(node.finished);
         if (inProgressTree.length === 0 && finishedTree.length === 0) return null;
         return (
           <ul className="d-inline-block align-top">
-            {node.inProgress.edges.length > 0 && (
+            {compact(node.inProgress.edges ?? []).length > 0 && (
               <li key={`inprogress-${node.id}`}>
                 <b>{`${node.name}`}</b>
                 : In progress
@@ -1968,7 +1988,7 @@ const MyGrading: React.FC<{
                 />
               </li>
             )}
-            {node.finished.edges.length > 0 && (
+            {compact(node.finished.edges ?? []).length > 0 && (
               <li key={`finished-${node.id}`}>
                 <b>{`${node.name}`}</b>
                 : Finished
@@ -2010,8 +2030,8 @@ const BeginGradingButton: React.FC<{
     examKey,
   );
 
-  const { examVersions } = res;
-  const completionStats = examVersions.edges.map(({ node }) => node.completionSummary as {
+  const examVersions = compact(res.examVersions.edges?.map((e) => e?.node) ?? []);
+  const completionStats = examVersions.map((node) => node.completionSummary as {
     notStarted: number;
     inProgress: number;
     finished: number;
@@ -2027,7 +2047,8 @@ const BeginGradingButton: React.FC<{
           registrationId,
           qnum,
           pnum,
-        } = gradeNext;
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        } = gradeNext!;
         history.push(`/exams/${examId}/grading/${registrationId}/${qnum}/${pnum}`);
       },
       onError: (err) => {
@@ -2040,12 +2061,12 @@ const BeginGradingButton: React.FC<{
       },
     },
   );
-  const filtered = examVersions.edges.filter((_ver, index) => !allBlank(completionStats[index]));
+  const filtered = examVersions.filter((_ver, index) => !allBlank(completionStats[index]));
   const filteredCompletionStats = completionStats.filter((ver) => !allBlank(ver));
   const chunkSize = 4;
   const versionsInChunks = Array.from(
     { length: Math.ceil(filtered.length / chunkSize) },
-    (v, i) => filtered.slice(i * chunkSize, i * chunkSize + chunkSize),
+    (_v, i) => filtered.slice(i * chunkSize, i * chunkSize + chunkSize),
   );
   return (
     <div>
@@ -2077,7 +2098,7 @@ const BeginGradingButton: React.FC<{
                 // eslint-disable-next-line react/no-array-index-key
                 key={chunkIndex}
               >
-                {chunk.map(({ node }, nodeIndex) => {
+                {chunk.map((node, nodeIndex) => {
                   const index = chunkIndex * chunkSize + nodeIndex;
                   return (
                     // eslint-disable-next-line react/no-array-index-key
@@ -2113,7 +2134,7 @@ const BeginGradingButton: React.FC<{
           </div>
         </Dropdown.Menu>
       </Dropdown>
-      {examVersions.edges.map(({ node }, index) => (
+      {examVersions.map((node, index) => (
         <ul key={node.id} className="d-inline-block align-top">
           <li>
             {node.name}
@@ -2284,7 +2305,7 @@ const VersionLocks: React.FC<{
         </tr>
       </thead>
       <tbody>
-        {version.gradingLocks.edges.map(({ node }) => (
+        {compact(version.gradingLocks.edges?.map((e) => e?.node) ?? []).map((node) => (
           <GradingLock key={node.id} lockKey={node} />
         ))}
       </tbody>
@@ -2444,7 +2465,7 @@ const ExamGradingAdministration: React.FC<{
   );
   return (
     <>
-      {res.examVersions.edges.map(({ node }) => (
+      {compact(res.examVersions.edges?.map((e) => e?.node) ?? []).map((node) => (
         <VersionAdministration key={node.id} versionKey={node} />
       ))}
       {res.graded && (
diff --git a/app/javascript/components/workflows/grading/questions/ObjectiveGrade.tsx b/app/javascript/components/workflows/grading/questions/ObjectiveGrade.tsx
index 5252f4e1f..1828ecebb 100644
--- a/app/javascript/components/workflows/grading/questions/ObjectiveGrade.tsx
+++ b/app/javascript/components/workflows/grading/questions/ObjectiveGrade.tsx
@@ -10,7 +10,7 @@ interface ObjectiveGradeProps {
 }
 const ObjectiveGrade: React.FC<ObjectiveGradeProps> = (props) => {
   const { className } = props;
-  const [value, setValue] = useState<boolean>(undefined);
+  const [value, setValue] = useState<boolean | undefined>(undefined);
   return (
     <ToggleButtonGroup
       name="correctness"
diff --git a/app/javascript/components/workflows/home/index.tsx b/app/javascript/components/workflows/home/index.tsx
index 66c53c0bd..f6c59a17c 100644
--- a/app/javascript/components/workflows/home/index.tsx
+++ b/app/javascript/components/workflows/home/index.tsx
@@ -21,7 +21,7 @@ import {
 } from 'react-bootstrap';
 import { DateTime } from 'luxon';
 import LinkButton from '@hourglass/common/linkbutton';
-import { SelectOption } from '@hourglass/common/helpers';
+import { SelectOption, compact } from '@hourglass/common/helpers';
 import { AlertContext } from '@hourglass/common/alerts';
 import Icon from '@student/exams/show/components/Icon';
 import { MdPerson } from 'react-icons/md';
@@ -312,7 +312,7 @@ export const ImpersonateUser: React.FC<{
       },
     },
   );
-  const [selectedUser, setSelectedUser] = useState<string>(undefined);
+  const [selectedUser, setSelectedUser] = useState<string | undefined>(undefined);
   return (
     <>
       <Row>
@@ -488,13 +488,18 @@ const Home: React.FC = () => {
         )}
         <div>
           {res.data.activeTerms.map((term) => {
+            const myStaffRegistrations = compact(term.myStaffRegistrations.nodes ?? []);
+            const myProctorRegistrations = compact(term.myProctorRegistrations.nodes ?? []);
+            const myProfessorCourseRegistrations = compact(
+              term.myProfessorCourseRegistrations.nodes ?? [],
+            );
             const allEmpty = (
               term.myFutureRegistrations.length === 0
               && term.myRegistrations.length === 0
               && term.myPriorRegistrations.length === 0
-              && term.myStaffRegistrations.nodes.length === 0
-              && term.myProctorRegistrations.nodes.length === 0
-              && term.myProfessorCourseRegistrations.nodes.length === 0
+              && myStaffRegistrations.length === 0
+              && myProctorRegistrations.length === 0
+              && myProfessorCourseRegistrations.length === 0
             );
             return (
               <Card className="my-3" key={`home-term-${term.id}`}>
@@ -517,13 +522,13 @@ const Home: React.FC = () => {
                     registrations={term.myPriorRegistrations}
                   />
                   <ShowProctorRegs
-                    proctorRegistrations={term.myProctorRegistrations.nodes}
+                    proctorRegistrations={myProctorRegistrations}
                   />
                   <ShowStaffRegs
-                    staffRegistrations={term.myStaffRegistrations.nodes}
+                    staffRegistrations={myStaffRegistrations}
                   />
                   <ShowProfRegs
-                    professorCourseRegistrations={term.myProfessorCourseRegistrations.nodes}
+                    professorCourseRegistrations={myProfessorCourseRegistrations}
                   />
                 </Card.Body>
               </Card>
diff --git a/app/javascript/components/workflows/index.tsx b/app/javascript/components/workflows/index.tsx
index 6010a3133..ee2e86652 100644
--- a/app/javascript/components/workflows/index.tsx
+++ b/app/javascript/components/workflows/index.tsx
@@ -93,7 +93,7 @@ export const BlockNav: React.FC<{
 const Entry: React.FC = () => {
   const [transitioning, setTransitioning] = useState(false);
   const [transitionMessage, setTransitionMessage] = useState('');
-  const [transitionCallback, setTransitionCallback] = useState(() => (_) => undefined);
+  const [transitionCallback, setTransitionCallback] = useState(() => (_): void => undefined);
   const [cancelText, setCancelText] = useState<string>('Stay');
   const [leaveText, setLeaveText] = useState<string>('Leave');
   const [customHandler, setCustomHandler] = useState<CustomHandler>(() => (_) => undefined);
diff --git a/app/javascript/components/workflows/proctor/exams/index.tsx b/app/javascript/components/workflows/proctor/exams/index.tsx
index 886722273..bb6a5ad98 100644
--- a/app/javascript/components/workflows/proctor/exams/index.tsx
+++ b/app/javascript/components/workflows/proctor/exams/index.tsx
@@ -33,7 +33,12 @@ import { MdMessage, MdSend, MdPeople } from 'react-icons/md';
 import Loading from '@hourglass/common/loading';
 import { AlertContext } from '@hourglass/common/alerts';
 import TooltipButton from '@student/exams/show/components/TooltipButton';
-import { ExhaustiveSwitchError, SelectOption, SelectOptions } from '@hourglass/common/helpers';
+import {
+  ExhaustiveSwitchError,
+  SelectOption,
+  SelectOptions,
+  compact,
+} from '@hourglass/common/helpers';
 import { GiBugleCall } from 'react-icons/gi';
 import { DateTime } from 'luxon';
 import { IconType } from 'react-icons';
@@ -95,7 +100,7 @@ interface DirectMessage {
   };
   registration: {
     id: string;
-    room: {
+    room?: {
       id: string;
     };
     examVersion: {
@@ -115,7 +120,7 @@ interface Question {
   body: string;
   registration: {
     id: string;
-    room: {
+    room?: {
       id: string;
     };
     examVersion: {
@@ -513,11 +518,12 @@ const ShowAnomalies: React.FC<{
     }],
   }), [data.id]));
 
+  const anomalies = compact(data.anomalies.edges?.map((e) => e?.node) ?? []);
   return (
     <>
-      {data.anomalies.edges.length === 0 && <tr><td colSpan={4}>No anomalies.</td></tr>}
-      {data.anomalies.edges.map((edge) => (
-        <ShowAnomaly key={edge.node.id} replyTo={replyTo} examId={data.id} anomalyKey={edge.node} />
+      {anomalies.length === 0 && <tr><td colSpan={4}>No anomalies.</td></tr>}
+      {anomalies.map((node) => (
+        <ShowAnomaly key={node.id} replyTo={replyTo} examId={data.id} anomalyKey={node} />
       ))}
       {hasNext && (
         <tr>
@@ -528,7 +534,7 @@ const ShowAnomalies: React.FC<{
                 loadNext(
                   10,
                   {
-                    onComplete: (error?: Error) => {
+                    onComplete: (error: Error | null) => {
                       if (!error) return;
                       alert({
                         variant: 'danger',
@@ -616,7 +622,6 @@ export const FinalizeDialog: React.FC<{
 };
 
 const FinalizeRegs: React.FC<{
-  buttonText?: string;
   recipientOptions: RecipientOptions;
 }> = (props) => {
   const {
@@ -910,7 +915,7 @@ const ShowMessages: React.FC<{
   } = props;
   const [lastViewed, setLastViewed] = useState<DateTime>(DateTime.local());
   const resetLastViewed = useCallback(() => setLastViewed(DateTime.local()), []);
-  const [filter, setFilter] = useState<MessageFilterOption[]>(undefined);
+  const [filter, setFilter] = useState<MessageFilterOption[] | undefined>(undefined);
   let all: Array<Message> = [];
   if (!receivedOnly) {
     all = all
@@ -1469,35 +1474,35 @@ const ExamMessages: React.FC<{
     exam,
   );
   const response: Response = useMemo(() => ({
-    sent: res.messages.edges.map(({ node: msg }) => ({
+    sent: compact(res.messages.edges?.map((e) => e?.node) ?? []).map((msg) => ({
       type: MessageType.Direct,
       id: msg.id,
       body: msg.body,
       sender: msg.sender,
-      registration: msg.registration,
+      registration: { ...msg.registration, room: msg.registration.room ?? undefined },
       time: DateTime.fromISO(msg.createdAt),
     })),
-    studentQuestions: res.studentQuestions.edges.map(({ node: question }) => ({
+    studentQuestions: compact(res.studentQuestions.edges?.map((e) => e?.node) ?? []).map((q) => ({
       type: MessageType.Question,
-      id: question.id,
-      body: question.body,
-      registration: question.registration,
-      time: DateTime.fromISO(question.createdAt),
+      id: q.id,
+      body: q.body,
+      registration: { ...q.registration, room: q.registration.room ?? undefined },
+      time: DateTime.fromISO(q.createdAt),
     })),
-    version: res.versionAnnouncements.edges.map(({ node: va }) => ({
+    version: compact(res.versionAnnouncements.edges?.map((e) => e?.node) ?? []).map((va) => ({
       type: MessageType.Version,
       id: va.id,
       body: va.body,
       version: va.examVersion,
       time: DateTime.fromISO(va.createdAt),
     })),
-    exam: res.examAnnouncements.edges.map(({ node: ea }) => ({
+    exam: compact(res.examAnnouncements.edges?.map((e) => e?.node) ?? []).map((ea) => ({
       type: MessageType.Exam,
       id: ea.id,
       body: ea.body,
       time: DateTime.fromISO(ea.createdAt),
     })),
-    room: res.roomAnnouncements.edges.map(({ node: ra }) => ({
+    room: compact(res.roomAnnouncements.edges?.map((e) => e?.node) ?? []).map((ra) => ({
       type: MessageType.Room,
       id: ra.id,
       body: ra.body,
@@ -1681,7 +1686,7 @@ const SplitViewLoaded: React.FC<{
     recipients,
   } = props;
   const { alert } = useContext(AlertContext);
-  const messageRef = useRef<HTMLTextAreaElement>();
+  const messageRef = useRef<HTMLTextAreaElement>(null);
   const roomOptions: SelectOptions<Recipient> = recipients.rooms.map((r) => ({
     label: r.name,
     // This toString is needed because otherwise some CSS
@@ -1690,7 +1695,7 @@ const SplitViewLoaded: React.FC<{
     // since they're all [object Object]
     value: { ...r, toString: ((): string => r.id), type: MessageType.Room },
   }));
-  roomOptions.unshift({ label: 'No room', value: { type: MessageType.Room, id: undefined, name: 'No room' } });
+  roomOptions.unshift({ label: 'No room', value: { type: MessageType.Room, id: `No Room ${DateTime.now().toISO()}`, name: 'No room' } });
   const recipientOptions = useMemo<RecipientOptions>(() => ([
     {
       label: 'Entire exam',
@@ -1741,8 +1746,9 @@ const SplitViewLoaded: React.FC<{
         message: `Invalid registration ID: ${registrationId}`,
         copyButton: true,
       });
+    } else {
+      setSelectedRecipient(recip);
     }
-    setSelectedRecipient(recip);
     if (messageRef.current) messageRef.current.focus();
   };
   return (
@@ -1818,18 +1824,18 @@ const ProctoringSplitView: React.FC<{
       name: reg.user.displayName,
     };
     students.push(r);
-    studentsByRoom[reg.room?.id] = studentsByRoom[reg.room?.id] ?? {};
-    studentsByRoom[reg.room?.id][reg.id] = true;
+    studentsByRoom[reg.room?.id ?? ''] = studentsByRoom[reg.room?.id ?? ''] ?? {};
+    studentsByRoom[reg.room?.id ?? ''][reg.id] = true;
     studentsByVersion[reg.examVersion.id] = studentsByVersion[reg.examVersion.id] ?? {};
     studentsByVersion[reg.examVersion.id][reg.id] = true;
-    versionsByRoom[reg.room?.id] = versionsByRoom[reg.room?.id] ?? {};
-    versionsByRoom[reg.room?.id][reg.examVersion.id] = true;
+    versionsByRoom[reg.room?.id ?? ''] = versionsByRoom[reg.room?.id ?? ''] ?? {};
+    versionsByRoom[reg.room?.id ?? ''][reg.examVersion.id] = true;
     roomsByVersion[reg.examVersion.id] = roomsByVersion[reg.examVersion.id] ?? {};
-    roomsByVersion[reg.examVersion.id][reg.room?.id] = true;
+    roomsByVersion[reg.examVersion.id][reg.room?.id ?? ''] = true;
   });
   const sortByName = (a, b) => a.name.localeCompare(b.name);
   const recipients: SplitRecipients = useMemo(() => ({
-    versions: res.examVersions.edges.map(({ node: ev }) => {
+    versions: compact(res.examVersions.edges?.map((e) => e?.node) ?? []).map((ev) => {
       const r: Recipient = {
         type: MessageType.Version,
         id: ev.id,
diff --git a/app/javascript/components/workflows/proctor/registrations/show/DisplayBody.tsx b/app/javascript/components/workflows/proctor/registrations/show/DisplayBody.tsx
index a27084699..2622d46e6 100644
--- a/app/javascript/components/workflows/proctor/registrations/show/DisplayBody.tsx
+++ b/app/javascript/components/workflows/proctor/registrations/show/DisplayBody.tsx
@@ -1,4 +1,4 @@
-import React, { useContext, useState } from 'react';
+import React, { ReactElement, useContext, useState } from 'react';
 import { graphql, useFragment } from 'relay-hooks';
 import { ExamViewerContext } from '@hourglass/common/context';
 import DisplayCode from '@proctor/registrations/show/questions/DisplayCode';
@@ -37,7 +37,7 @@ import { DisplayBody$key } from './__generated__/DisplayBody.graphql';
 
 export interface BodyProps {
   bodyKey: DisplayBody$key;
-  refreshCodeMirrorsDeps: React.DependencyList;
+  refreshCodeMirrorsDeps?: React.DependencyList;
   qnum: number;
   pnum: number;
   bnum: number;
@@ -66,7 +66,7 @@ const ShowComment: React.FC<{ comment: CommentJson }> = (props) => {
   );
 };
 
-const ShowRubricPreset: React.FC<{ preset: RubricPresetJson, points: number}> = (props) => {
+const ShowRubricPreset: React.FC<{ preset: RubricPresetJson, points?: number}> = (props) => {
   const { preset, points } = props;
   const { info, values } = preset;
   const { label, direction } = info;
@@ -191,7 +191,7 @@ const DisplayBody: React.FC<BodyProps> = (props) => {
     case 'HTML':
       return <HTML value={body.info} />;
     case 'Code': {
-      let initial = null;
+      let initial: ReactElement | undefined;
       if (overviewMode && body.info.initial) {
         initial = (
           <Card bg="secondary" border="info" className="mt-2 mb-3">
@@ -209,7 +209,7 @@ const DisplayBody: React.FC<BodyProps> = (props) => {
                 <DisplayCode
                   info={body.info}
                   value={null}
-                  refreshProps={[...refreshCodeMirrorsDeps, open]}
+                  refreshProps={[...(refreshCodeMirrorsDeps ?? []), open]}
                   fullyExpandCode={fullyExpandCode}
                 />
               </Card.Body>
diff --git a/app/javascript/components/workflows/proctor/registrations/show/Part.tsx b/app/javascript/components/workflows/proctor/registrations/show/Part.tsx
index 083e1a58f..bb746686b 100644
--- a/app/javascript/components/workflows/proctor/registrations/show/Part.tsx
+++ b/app/javascript/components/workflows/proctor/registrations/show/Part.tsx
@@ -17,13 +17,13 @@ import { PartRequestGradingLockMutation } from './__generated__/PartRequestGradi
 import { PartShow$key } from './__generated__/PartShow.graphql';
 
 interface PartProps {
-  refreshCodeMirrorsDeps: React.DependencyList;
+  refreshCodeMirrorsDeps?: React.DependencyList;
   partKey: PartShow$key;
   qnum: number;
   pnum: number;
   currentGrading?: CurrentGrading[number][number];
   anonymous?: boolean;
-  showRequestGrading?: string;
+  showRequestGrading?: string | null;
   fullyExpandCode?: boolean;
   overviewMode: boolean;
 }
@@ -109,7 +109,7 @@ const Part: React.FC<PartProps> = (props) => {
     qnum,
     pnum,
     currentGrading,
-    anonymous,
+    anonymous = false,
     showRequestGrading = false,
     fullyExpandCode = false,
     overviewMode,
@@ -164,7 +164,7 @@ const Part: React.FC<PartProps> = (props) => {
     <PartFilesContext.Provider value={contextVal}>
       <div>
         <h3 id={`question-${qnum}-part-${pnum}`} className="d-flex align-items-baseline">
-          <PartName anonymous={anonymous} name={name} pnum={pnum} />
+          <PartName anonymous={anonymous} name={name ?? undefined} pnum={pnum} />
           <span className="ml-auto">
             {anonymous || (
               <span className="point-count">
diff --git a/app/javascript/components/workflows/proctor/registrations/show/ShowQuestion.tsx b/app/javascript/components/workflows/proctor/registrations/show/ShowQuestion.tsx
index ebc8ee667..e4ed5a3a3 100644
--- a/app/javascript/components/workflows/proctor/registrations/show/ShowQuestion.tsx
+++ b/app/javascript/components/workflows/proctor/registrations/show/ShowQuestion.tsx
@@ -11,7 +11,7 @@ import { pluralize } from '@hourglass/common/helpers';
 import { ShowQuestion$key } from './__generated__/ShowQuestion.graphql';
 
 interface ShowQuestionProps {
-  refreshCodeMirrorsDeps: React.DependencyList;
+  refreshCodeMirrorsDeps?: React.DependencyList;
   questionKey: ShowQuestion$key,
   qnum: number;
   currentGrading?: CurrentGrading[number];
@@ -67,9 +67,9 @@ const ShowQuestion: React.FC<ShowQuestionProps> = (props) => {
   const singlePart = parts.length === 1 && !parts[0].name?.value?.trim();
   const points = parts.reduce((pts, p, _idx) => pts + p.points, 0);
   const strPoints = pluralize(points, 'point', 'points');
-  let curScore = 0;
+  let curScore: number | undefined = 0;
   for (let i = 0; i < parts.length; i += 1) {
-    if (currentGrading[i]?.score !== undefined) {
+    if (currentGrading[i]?.score !== undefined && curScore !== undefined) {
       curScore += currentGrading[i].score;
     } else {
       curScore = undefined;
@@ -86,7 +86,7 @@ const ShowQuestion: React.FC<ShowQuestionProps> = (props) => {
     <QuestionFilesContext.Provider value={contextVal}>
       <div>
         <h1 id={`question-${qnum}`} className="d-flex align-items-baseline">
-          <QuestionName name={name} qnum={qnum} />
+          <QuestionName name={name ?? undefined} qnum={qnum} />
           {singlePart && (
             <span className="ml-auto">
               <span className="point-count">
@@ -107,7 +107,7 @@ const ShowQuestion: React.FC<ShowQuestionProps> = (props) => {
             </span>
           )}
         </h1>
-        <HTML value={description} />
+        <HTML value={description ?? undefined} />
         {references.length !== 0 && (
           <FileViewer
             references={references}
diff --git a/app/javascript/components/workflows/proctor/registrations/show/index.tsx b/app/javascript/components/workflows/proctor/registrations/show/index.tsx
index 8d9e04adf..5b6f33675 100644
--- a/app/javascript/components/workflows/proctor/registrations/show/index.tsx
+++ b/app/javascript/components/workflows/proctor/registrations/show/index.tsx
@@ -20,7 +20,7 @@ import { showExamViewer$key } from './__generated__/showExamViewer.graphql';
 interface ExamViewerProps {
   version: showExamViewer$key;
   currentGrading?: CurrentGrading;
-  currentAnswers?: AnswersState;
+  currentAnswers: AnswersState;
   refreshCodeMirrorsDeps?: React.DependencyList;
   registrationId?: string;
   overviewMode: boolean;
@@ -140,7 +140,7 @@ const ExamViewer: React.FC<ExamViewerProps> = (props) => {
                 references={references}
               />
             )}
-            {overviewMode && <ShowRubricKey rubricKey={res.rootRubric} forWhat="exam" />}
+            {overviewMode && res.rootRubric && <ShowRubricKey rubricKey={res.rootRubric} forWhat="exam" />}
             <div>
               <DisplayQuestions
                 refreshCodeMirrorsDeps={refreshCodeMirrorsDeps}
diff --git a/app/javascript/components/workflows/proctor/registrations/show/questions/DisplayCode.tsx b/app/javascript/components/workflows/proctor/registrations/show/questions/DisplayCode.tsx
index a884a57a9..6548e82c6 100644
--- a/app/javascript/components/workflows/proctor/registrations/show/questions/DisplayCode.tsx
+++ b/app/javascript/components/workflows/proctor/registrations/show/questions/DisplayCode.tsx
@@ -5,7 +5,7 @@ import { ExamContext } from '@hourglass/common/context';
 
 interface CodeProps {
   info: CodeInfo;
-  value?: CodeState;
+  value?: CodeState | null;
   refreshProps?: React.DependencyList;
   fullyExpandCode?: boolean;
 }
diff --git a/app/javascript/components/workflows/professor/courses/sync.tsx b/app/javascript/components/workflows/professor/courses/sync.tsx
index a5f0f1835..d4a747a92 100644
--- a/app/javascript/components/workflows/professor/courses/sync.tsx
+++ b/app/javascript/components/workflows/professor/courses/sync.tsx
@@ -36,11 +36,20 @@ const DoSync: React.FC<{
     `,
     {
       onCompleted: ({ syncCourseToBottlenose }) => {
-        alert({
-          variant: 'success',
-          title: 'Course synced',
-          message: `${syncCourseToBottlenose.course.title} was synced successfully.`,
-        });
+        if (syncCourseToBottlenose) {
+          alert({
+            variant: 'success',
+            title: 'Course synced',
+            message: `${syncCourseToBottlenose.course.title} was synced successfully.`,
+          });
+        } else {
+          alert({
+            variant: 'danger',
+            title: 'Error syncing course',
+            message: 'No data received from server',
+            copyButton: true,
+          });
+        }
       },
       onError: (err) => {
         alert({
diff --git a/app/javascript/components/workflows/professor/exams/accommodations/index.tsx b/app/javascript/components/workflows/professor/exams/accommodations/index.tsx
index a75434374..c4a3fc5f9 100644
--- a/app/javascript/components/workflows/professor/exams/accommodations/index.tsx
+++ b/app/javascript/components/workflows/professor/exams/accommodations/index.tsx
@@ -13,7 +13,7 @@ import ReadableDate from '@hourglass/common/ReadableDate';
 import { NumericInput } from '@hourglass/common/NumericInput';
 import { BsPencilSquare } from 'react-icons/bs';
 import { AlertContext } from '@hourglass/common/alerts';
-import { SelectOption, SelectOptions } from '@hourglass/common/helpers';
+import { SelectOption, SelectOptions, compact } from '@hourglass/common/helpers';
 import { FaTrash } from 'react-icons/fa';
 import Select from 'react-select';
 import { DateTime } from 'luxon';
@@ -28,9 +28,9 @@ import { accommodationsDestroyMutation } from './__generated__/accommodationsDes
 
 const AccommodationEditor: React.FC<{
   disabled?: boolean;
-  submit: (startTime: DateTime, extraTime: number) => void;
+  submit: (startTime: DateTime | undefined, extraTime: number) => void;
   cancel: () => void;
-  newStartTime: DateTime;
+  newStartTime?: DateTime;
   percentTimeExpansion: number;
   displayName: string;
 }> = (props) => {
@@ -202,7 +202,7 @@ const SingleAccommodation: React.FC<{
       },
     },
   );
-  const submit = (newStartTime: DateTime, percentTimeExpansion: number) => {
+  const submit = (newStartTime: DateTime | undefined, percentTimeExpansion: number) => {
     update({
       variables: {
         input: {
@@ -284,7 +284,7 @@ const NewAccommodation: React.FC<{
   const {
     exam,
   } = props;
-  const [selected, setSelected] = useState<Selection>(null);
+  const [selected, setSelected] = useState<Selection | null>(null);
   const { alert } = useContext(AlertContext);
   const regsNoAccommodation = useFragment(
     graphql`
@@ -304,11 +304,11 @@ const NewAccommodation: React.FC<{
     `,
     exam,
   );
-  const sorted: SelectOptions<string> = [
-    ...regsNoAccommodation.registrationsWithoutAccommodation.edges,
-  ].sort(
-    (a, b) => a.node.user.displayName.localeCompare(b.node.user.displayName),
-  ).map(({ node }) => ({
+  const sorted: SelectOptions<string> = compact(
+    regsNoAccommodation.registrationsWithoutAccommodation.edges?.map((e) => e?.node) ?? [],
+  ).sort(
+    (a, b) => a.user.displayName.localeCompare(b.user.displayName),
+  ).map((node) => ({
     label: node.user.displayName,
     value: node.id,
   }));
@@ -335,7 +335,7 @@ const NewAccommodation: React.FC<{
           variant: 'success',
           title: 'Successfully created accommodation',
           autohide: true,
-          message: `Accommodation for '${selected.label}' created.`,
+          message: `Accommodation for '${selected?.label}' created.`,
         });
       },
       onError: (err) => {
@@ -431,9 +431,9 @@ const ManageAccommodations: React.FC<{
     exam,
   );
   const { accommodations } = res;
-  const sorted = [...accommodations.edges].sort(
-    (a, b) => a.node.registration.user.displayName.localeCompare(
-      b.node.registration.user.displayName,
+  const sorted = compact(accommodations.edges?.map((e) => e?.node) ?? []).sort(
+    (a, b) => a.registration.user.displayName.localeCompare(
+      b.registration.user.displayName,
     ),
   );
   return (
@@ -450,11 +450,11 @@ const ManageAccommodations: React.FC<{
             </tr>
           </thead>
           <tbody>
-            {sorted.map((edge) => (
+            {sorted.map((node) => (
               <SingleAccommodation
                 examId={res.id}
-                key={edge.node.id}
-                accommodationKey={edge.node}
+                key={node.id}
+                accommodationKey={node}
               />
             ))}
           </tbody>
diff --git a/app/javascript/components/workflows/professor/exams/admin.tsx b/app/javascript/components/workflows/professor/exams/admin.tsx
index c1e7c2028..53c0b05a0 100644
--- a/app/javascript/components/workflows/professor/exams/admin.tsx
+++ b/app/javascript/components/workflows/professor/exams/admin.tsx
@@ -14,7 +14,7 @@ import {
   useLocation,
   Link,
 } from 'react-router-dom';
-import { pluralize, useRefresher } from '@hourglass/common/helpers';
+import { pluralize, useRefresher, compact } from '@hourglass/common/helpers';
 import { NumericInput } from '@hourglass/common/NumericInput';
 import {
   Card,
@@ -539,7 +539,7 @@ export const ExamInfoEditor: React.FC<{
               disabled={disabled}
               value={start}
               maxValue={end}
-              onChange={setStart}
+              onChange={(newVal) => setStart(newVal ?? defaultStartTime)}
             />
           </Col>
         </Form.Group>
@@ -550,7 +550,7 @@ export const ExamInfoEditor: React.FC<{
               disabled={disabled}
               value={end}
               minValue={start}
-              onChange={setEnd}
+              onChange={(newVal) => setEnd(newVal ?? defaultEndTime)}
             />
           </Col>
         </Form.Group>
@@ -634,6 +634,7 @@ const VersionInfo: React.FC<{
             hidden
             onChange={(event) => {
               const { files } = event.target;
+              if (!files) return;
               const [f] = files;
               if (!f) return;
               uploadFile<{ id: number; }>(res.examVersionUploadUrl, f).then((innerRes) => {
@@ -658,7 +659,7 @@ const VersionInfo: React.FC<{
             className="mr-2"
             variant="success"
             onClick={(): void => {
-              fileInputRef.current.click();
+              fileInputRef.current?.click();
             }}
           >
             Import Version
@@ -681,7 +682,7 @@ const VersionInfo: React.FC<{
         </div>
       </h2>
       <ul>
-        {res.examVersions.edges.map(({ node: version }) => (
+        {compact(res.examVersions.edges?.map((e) => e?.node) ?? []).map((version) => (
           <li key={version.id}>
             <ShowVersion
               examId={res.id}
@@ -863,6 +864,7 @@ const PreviewVersion: React.FC<{
         <div className="border p-2">
           <ExamViewer
             version={res}
+            currentAnswers={{ answers: [], scratch: '' }}
             overviewMode
             refreshCodeMirrorsDeps={[open]}
           />
diff --git a/app/javascript/components/workflows/professor/exams/allocate-versions.tsx b/app/javascript/components/workflows/professor/exams/allocate-versions.tsx
index 37b251cda..9016fb8db 100644
--- a/app/javascript/components/workflows/professor/exams/allocate-versions.tsx
+++ b/app/javascript/components/workflows/professor/exams/allocate-versions.tsx
@@ -15,6 +15,7 @@ import {
   WrappedFieldArrayProps,
   FormSection,
 } from 'redux-form';
+import { compact } from '@hourglass/common/helpers';
 import store from '@hourglass/common/student-dnd/store';
 import { Provider } from 'react-redux';
 import {
@@ -27,11 +28,14 @@ import { useFragment, graphql, useMutation } from 'relay-hooks';
 
 import { TabEditButton } from './admin';
 import { allocateVersions$key, allocateVersions } from './__generated__/allocateVersions.graphql';
-import { allocateVersionsMutation } from './__generated__/allocateVersionsMutation.graphql';
+import { allocateVersionsMutation, VersionAssignment } from './__generated__/allocateVersionsMutation.graphql';
+
+type NN<T> = Exclude<T, null>
+type O<T> = T | undefined
 
 type Section = allocateVersions['course']['sections'][number];
 type Student = allocateVersions['unassignedStudents'][number];
-type Version = allocateVersions['examVersions']['edges'][number]['node'];
+type Version = NN<NN<NN<allocateVersions['examVersions']['edges']>[number]>['node']>;
 
 interface FormContextType {
   sections: readonly Section[];
@@ -274,7 +278,7 @@ const StudentDNDForm: React.FC<
   return (
     <form
       onSubmit={handleSubmit(({ all }) => {
-        const versions = [];
+        const versions: VersionAssignment[] = [];
         all.versions.forEach((version) => {
           versions.push({
             versionId: version.id,
@@ -300,7 +304,7 @@ const StudentDNDForm: React.FC<
             <Button
               disabled={loading}
               variant="danger"
-              className={pristine && 'd-none'}
+              className={pristine ? 'd-none' : undefined}
               onClick={reset}
             >
               Reset
@@ -518,7 +522,7 @@ const DND: React.FC<{
       examId={res.id}
       sections={res.course.sections}
       unassigned={res.unassignedStudents}
-      versions={res.examVersions.edges.map((e) => e.node)}
+      versions={compact(res.examVersions.edges?.map((e) => e?.node) ?? [])}
     />
   );
 };
diff --git a/app/javascript/components/workflows/professor/exams/assign-staff/index.tsx b/app/javascript/components/workflows/professor/exams/assign-staff/index.tsx
index 1d33242e4..d507bf0dc 100644
--- a/app/javascript/components/workflows/professor/exams/assign-staff/index.tsx
+++ b/app/javascript/components/workflows/professor/exams/assign-staff/index.tsx
@@ -41,7 +41,7 @@ type ItemTypes = DropStudent;
 
 interface Student {
   id: string;
-  nuid: number;
+  nuid?: number;
   username: string;
   displayName: string;
 }
@@ -238,7 +238,9 @@ const StaffSeatingForm: React.FC<
         if (room.id === roomId) {
           return {
             ...room,
-            proctors: filtered.concat(section.staff),
+            proctors: filtered.concat(
+              section.staff.map((s) => ({ ...s, nuid: s.nuid ?? undefined })),
+            ),
           };
         }
         return {
@@ -315,7 +317,7 @@ const StaffSeatingForm: React.FC<
             <Button
               disabled={loading}
               variant="danger"
-              className={pristine && 'd-none'}
+              className={pristine ? 'd-none' : undefined}
               onClick={reset}
             >
               Reset
@@ -389,12 +391,14 @@ const Editable: React.FC<StaffAssignmentProps> = (props) => {
   const contextVal = useMemo(() => ({ sections }), [sections]);
   const initialValues = useMemo(() => ({
     all: {
-      unassigned,
-      proctors: proctors.map((p) => p.user),
+      unassigned: unassigned.map((u) => ({ ...u, nuid: u.nuid ?? undefined })),
+      proctors: proctors.map((p) => ({ ...p.user, nuid: p.user.nuid ?? undefined })),
       rooms: rooms.map((r) => ({
         id: r.id,
         name: r.name,
-        proctors: r.proctorRegistrations.map((p) => p.user),
+        proctors: r.proctorRegistrations.map(
+          (p) => ({ ...p.user, nuid: p.user.nuid ?? undefined }),
+        ),
       })),
     },
   }), [unassigned, proctors, rooms]);
diff --git a/app/javascript/components/workflows/professor/exams/new/DateTimePicker.tsx b/app/javascript/components/workflows/professor/exams/new/DateTimePicker.tsx
index 9c0c415fb..e8e2c96e5 100644
--- a/app/javascript/components/workflows/professor/exams/new/DateTimePicker.tsx
+++ b/app/javascript/components/workflows/professor/exams/new/DateTimePicker.tsx
@@ -19,7 +19,7 @@ interface DateTimeProps {
   value?: DateTime;
   minValue?: DateTime;
   maxValue?: DateTime;
-  onChange: (newVal: DateTime) => void;
+  onChange: (newVal: DateTime | undefined) => void;
   nullable?: boolean;
 }
 
@@ -96,7 +96,11 @@ const DateTimePicker: React.FC<DateTimeProps> = (props) => {
             maxDate={maxValue?.toJSDate()}
             onChange={(date, _event): void => {
               if (onChange) {
-                onChange(mergeDateTime(DateTime.fromJSDate(date), value ?? DateTime.local()));
+                if (date) {
+                  onChange(mergeDateTime(DateTime.fromJSDate(date), value ?? DateTime.local()));
+                } else {
+                  onChange(value ?? DateTime.local());
+                }
               }
             }}
           />
diff --git a/app/javascript/components/workflows/professor/exams/new/editor/FileUploader.tsx b/app/javascript/components/workflows/professor/exams/new/editor/FileUploader.tsx
index ae9246537..a26f308dd 100644
--- a/app/javascript/components/workflows/professor/exams/new/editor/FileUploader.tsx
+++ b/app/javascript/components/workflows/professor/exams/new/editor/FileUploader.tsx
@@ -25,11 +25,11 @@ const FileUploader: React.FC<{
     onChange,
   } = props;
   const noFiles = value === undefined || value.length === 0;
-  const [uploadedFileName, setUploadedFileName] = useState<string>(undefined);
+  const [uploadedFileName, setUploadedFileName] = useState<string | undefined>(undefined);
   const uploadLabel = noFiles ? 'Choose a file' : 'Saved files';
   const label = uploadedFileName ?? uploadLabel;
   const [open, setOpen] = useState(false);
-  const fileInput = useRef<HTMLInputElement>();
+  const fileInput = useRef<HTMLInputElement>(null);
   return (
     <Form.Group as={Row}>
       <Col sm={12}>
@@ -60,7 +60,9 @@ const FileUploader: React.FC<{
                 setUploadedFileName(undefined);
                 onChange([]);
                 if (fileInput.current) {
-                  fileInput.current.value = null;
+                  // Deliberately setting to null, to deal with weird browser issues
+                  // in resetting file inputs
+                  fileInput.current.value = null as unknown as string;
                 }
               }}
             >
diff --git a/app/javascript/components/workflows/professor/exams/new/editor/body-items/Code.tsx b/app/javascript/components/workflows/professor/exams/new/editor/body-items/Code.tsx
index fd92aa733..98e86893d 100644
--- a/app/javascript/components/workflows/professor/exams/new/editor/body-items/Code.tsx
+++ b/app/javascript/components/workflows/professor/exams/new/editor/body-items/Code.tsx
@@ -151,7 +151,8 @@ const EditCodeAnswerValues: React.FC<{
   } = props;
   const answerText = value?.text ?? '';
   const answerMarks = value?.marks ?? [];
-  const [instance, setInstance] = useState<CM.Editor>(undefined);
+  // Safe because this will be set before being used
+  const [instance, setInstance] = useState<CM.Editor | null>(null);
   const [lockState, setLockState] = useState<LockStateInfo>({
     enabled: false,
     active: false,
@@ -184,7 +185,7 @@ const EditCodeAnswerValues: React.FC<{
             onClick={(): void => {
               const newMarks = [...answerMarks];
               const { curRange, finalPos } = lockState;
-              if (lockState.active) {
+              if (lockState.active && curRange && instance) {
                 const markId = answerMarks.findIndex((m) => (
                   m.from.ch === curRange.from.ch
                   && m.from.line === curRange.from.line
@@ -192,7 +193,7 @@ const EditCodeAnswerValues: React.FC<{
                   && m.to.line === curRange.to.line
                 ));
                 removeMarks(instance, newMarks.splice(markId, 1));
-              } else {
+              } else if (curRange && finalPos && instance) {
                 const newMark: MarkDescription = {
                   from: {
                     ch: curRange.from.ch,
@@ -294,7 +295,7 @@ const SetInitial: React.FC<{
   initial: CodeInfo['initial'];
   lang: CodeInfo['lang'];
   disabled?: boolean;
-  onChangeInitial: (newVal: CodeInfo['initial']) => void;
+  onChangeInitial: (newVal: CodeInfo['initial'] | null) => void;
   onChangeLang: (newVal: CodeInfo['lang']) => void;
 }> = (props) => {
   const {
@@ -395,7 +396,7 @@ const Code: React.FC<{
       },
     });
   }, [id]);
-  const updateInitial = useCallback((newInitial: CodeInitial) => {
+  const updateInitial = useCallback((newInitial: CodeInitial | null) => {
     if (newInitial === null) {
       mutate({
         variables: {
diff --git a/app/javascript/components/workflows/professor/exams/new/editor/components/CustomEditor.tsx b/app/javascript/components/workflows/professor/exams/new/editor/components/CustomEditor.tsx
index f07d787c7..0dade576a 100644
--- a/app/javascript/components/workflows/professor/exams/new/editor/components/CustomEditor.tsx
+++ b/app/javascript/components/workflows/professor/exams/new/editor/components/CustomEditor.tsx
@@ -78,7 +78,7 @@ const CustomEditor: React.FC<CustomEditorProps> = ((props) => {
     }
   }, [onChange]);
 
-  const ref = useRef<ReactQuill>();
+  const ref = useRef<ReactQuill>(null);
   useEffect(() => {
     if (!ref.current) { return; }
     const rootDataset = ref.current.getEditor().root.dataset;
diff --git a/app/javascript/components/workflows/professor/exams/new/editor/index.tsx b/app/javascript/components/workflows/professor/exams/new/editor/index.tsx
index a3cbfba1b..f3229f787 100644
--- a/app/javascript/components/workflows/professor/exams/new/editor/index.tsx
+++ b/app/javascript/components/workflows/professor/exams/new/editor/index.tsx
@@ -250,7 +250,7 @@ const ExamVersionEditor: React.FC = () => {
       title: 'Students have already started taking this version',
       message: 'Changing the questions will likely result in nonsensical answers, and changing the structure of this version will result in undefined behavior. Be careful!',
     },
-    res.data?.examVersion?.anyStarted || res.data?.examVersion?.anyFinalized,
+    res.data?.examVersion?.anyStarted || res.data?.examVersion?.anyFinalized || false,
     [res.data?.examVersion?.anyStarted || res.data?.examVersion?.anyFinalized],
   );
   const [showRubrics, setShowRubrics] = useState(false);
diff --git a/app/javascript/components/workflows/professor/exams/submissions/index.tsx b/app/javascript/components/workflows/professor/exams/submissions/index.tsx
index 3a82f6d90..cf86cded0 100644
--- a/app/javascript/components/workflows/professor/exams/submissions/index.tsx
+++ b/app/javascript/components/workflows/professor/exams/submissions/index.tsx
@@ -122,6 +122,7 @@ const ExamSubmissions: React.FC = () => {
     weekday: 'short', month: 'short', day: '2-digit', hour: '2-digit', minute: '2-digit', second: '2-digit',
   };
   const lastStudentFinishTime = groups.started.reduce((latestSoFar, cur) => {
+    if (!cur.effectiveEndTime) return latestSoFar;
     const currentDateTime = DateTime.fromISO(cur.effectiveEndTime);
     if (currentDateTime > latestSoFar) {
       return currentDateTime;
@@ -231,7 +232,9 @@ const ExamSubmissions: React.FC = () => {
           </thead>
           <tbody>
             {groups.started.map((reg) => {
-              const timeDiff = DateTime.fromISO(reg.effectiveEndTime).diff(DateTime.local());
+              const timeDiff = reg.effectiveEndTime ? (
+                DateTime.fromISO(reg.effectiveEndTime).diff(DateTime.local())
+              ) : undefined;
               return (
                 <tr key={reg.id}>
                   <td>
@@ -251,7 +254,7 @@ const ExamSubmissions: React.FC = () => {
                     )}
                   </td>
                   <td>
-                    {describeRemainingTime(timeDiff)}
+                    {timeDiff && describeRemainingTime(timeDiff)}
                   </td>
                 </tr>
               );
@@ -300,7 +303,7 @@ const ExamSubmission: React.FC = () => {
   if (res.error) {
     return <RenderError error={res.error} />;
   }
-  if (!res.data) {
+  if (!res.data?.registration) {
     return <p>Loading...</p>;
   }
   const myRegistration = res.data.me.id === res.data.registration.user.id;
@@ -354,7 +357,7 @@ const ExamSubmissionStudent: React.FC = () => {
   if (res.error) {
     return <RenderError error={res.error} />;
   }
-  if (!res.data) {
+  if (!res.data?.registration) {
     return <p>Loading...</p>;
   }
   const { registration } = res.data;
@@ -372,7 +375,7 @@ const ExamSubmissionStudent: React.FC = () => {
       <h1>
         {`Submission by ${userInfo}`}
       </h1>
-      <h2>{`Grade: ${round(currentScorePercentage, 2).toFixed(2)}%`}</h2>
+      <h2>{currentScorePercentage !== null && `Grade: ${round(currentScorePercentage, 2).toFixed(2)}%`}</h2>
       <ExamViewerStudent
         version={registration.examVersion}
         currentGrading={currentGrading as CurrentGrading}
@@ -406,11 +409,11 @@ const ExamSubmissionStaff: React.FC = () => {
     `,
     { registrationId, withRubric: true },
   );
-  const [title, setTitle] = useState<string>(undefined);
+  const [title, setTitle] = useState<string | undefined>(undefined);
   if (res.error) {
     return <RenderError error={res.error} />;
   }
-  if (!res.data) {
+  if (!res.data?.registration) {
     return <p>Loading...</p>;
   }
   const { registration } = res.data;
@@ -434,7 +437,7 @@ const ExamSubmissionStaff: React.FC = () => {
     );
   }
   return (
-    <DocumentTitle title={title}>
+    <DocumentTitle title={title ?? `${exam.name} -- Submission for ${titleInfo}`}>
       <h1>
         {'Submission by '}
         {(published ? userInfo : (
@@ -446,7 +449,7 @@ const ExamSubmissionStaff: React.FC = () => {
           />
         ))}
       </h1>
-      {published && (
+      {published && currentScorePercentage !== null && (
         <h2>{`Grade: ${round(currentScorePercentage, 2).toFixed(2)}%`}</h2>
       )}
       <ExamViewer
diff --git a/app/javascript/components/workflows/student/exams/show/components/ExamCodeBox.tsx b/app/javascript/components/workflows/student/exams/show/components/ExamCodeBox.tsx
index 8290c89ac..b3fbe64d3 100644
--- a/app/javascript/components/workflows/student/exams/show/components/ExamCodeBox.tsx
+++ b/app/javascript/components/workflows/student/exams/show/components/ExamCodeBox.tsx
@@ -113,7 +113,7 @@ export const Editor: React.FC<EditorProps> = (props) => {
   } = props;
 
   // keep track of codemirror instance
-  const [instance, setInstance] = useState<CM.Editor>(undefined);
+  const [instance, setInstance] = useState<CM.Editor | null>(null);
 
   // whether to enable saving state to redux
   // this boolean is purposefully local to this specific render:
diff --git a/app/javascript/components/workflows/student/exams/show/components/ExamShowContents.tsx b/app/javascript/components/workflows/student/exams/show/components/ExamShowContents.tsx
index 5919b41f3..395494a76 100644
--- a/app/javascript/components/workflows/student/exams/show/components/ExamShowContents.tsx
+++ b/app/javascript/components/workflows/student/exams/show/components/ExamShowContents.tsx
@@ -56,12 +56,12 @@ const ExamShowContents: React.FC<ExamShowContentsProps> = (props) => {
     examKey,
   );
   const [showWarningModal, setShowWarningModal] = useState(false);
-  const [warningModalReason, setWarningModalReason] = useState<string>(undefined);
+  const [warningModalReason, setWarningModalReason] = useState<string | undefined>(undefined);
   const warnOnAnomaly = (reason: string) => {
     setWarningModalReason(reason);
     setShowWarningModal(true);
   };
-  const policies = res.myRegistration.examVersion.policies as readonly Policy[];
+  const policies = (res.myRegistration?.examVersion.policies ?? []) as readonly Policy[];
   const cleanupBeforeSubmit = useAnomalyListeners(
     res.takeUrl,
     policies,
@@ -79,7 +79,7 @@ const ExamShowContents: React.FC<ExamShowContentsProps> = (props) => {
   const {
     questions,
     instructions,
-    references,
+    references = [],
     files,
   } = exam;
   const examContextVal = useMemo(() => ({
diff --git a/app/javascript/components/workflows/student/exams/show/components/FileViewer.tsx b/app/javascript/components/workflows/student/exams/show/components/FileViewer.tsx
index 7b4a047ca..d9aeae471 100644
--- a/app/javascript/components/workflows/student/exams/show/components/FileViewer.tsx
+++ b/app/javascript/components/workflows/student/exams/show/components/FileViewer.tsx
@@ -52,7 +52,7 @@ export const Files: React.FC<FilesProps> = (props) => {
 };
 
 interface FileContentsProps {
-  selectedFile: string;
+  selectedFile?: string;
   selectedLine?: number;
   onChangeLine?: (lineNum: number) => void;
   refreshProps?: React.DependencyList;
@@ -69,8 +69,8 @@ const FileContents: React.FC<FileContentsProps> = (props) => {
     fmap,
     fullyExpandCode = false,
   } = props;
-  const f = fmap[selectedFile];
-  let cursor: CodeMirror.Position;
+  const f = selectedFile ? fmap[selectedFile] : undefined;
+  let cursor: CodeMirror.Position | undefined;
   if (selectedLine) {
     cursor = {
       line: selectedLine - 1,
@@ -122,7 +122,8 @@ const FileContents: React.FC<FileContentsProps> = (props) => {
 
 interface FileTreeProps {
   files: ExamFile[];
-  selectedFile: string;
+  // null so that the property stays controlled: undefined would get dropped from the props
+  selectedFile?: string | null;
   onChangeFile: (id: string) => void;
   fmap: FileMap;
   disabled?: boolean;
@@ -139,7 +140,7 @@ const FileTree: React.FC<FileTreeProps> = (props) => {
   const allIds = Object.keys(fmap);
   return (
     <TreeView
-      selected={selectedFile}
+      selected={selectedFile as (string | undefined)}
       disableSelection={disabled}
       onNodeSelect={(e, id): void => {
         const dir = fmap[id].filedir === 'dir';
@@ -203,7 +204,7 @@ interface ControlledFileViewerProps {
   alwaysShowTreeView?: boolean;
   selection?: CodeTagState;
   onChangeLine: (lineNumber: number) => void;
-  onChangeFile: (file: string) => void;
+  onChangeFile: (file: string | undefined) => void;
   refreshProps?: React.DependencyList;
 }
 
diff --git a/app/javascript/components/workflows/student/exams/show/components/HTML.tsx b/app/javascript/components/workflows/student/exams/show/components/HTML.tsx
index 509078781..13ad7a417 100644
--- a/app/javascript/components/workflows/student/exams/show/components/HTML.tsx
+++ b/app/javascript/components/workflows/student/exams/show/components/HTML.tsx
@@ -2,7 +2,7 @@ import React from 'react';
 import { HTMLVal } from '@student/exams/show/types';
 
 export interface HTMLProps {
-  value: HTMLVal;
+  value?: HTMLVal;
   className?: string;
 }
 
diff --git a/app/javascript/components/workflows/student/exams/show/components/navbar/ExamMessages.tsx b/app/javascript/components/workflows/student/exams/show/components/navbar/ExamMessages.tsx
index e4f187e4c..fc1119c9e 100644
--- a/app/javascript/components/workflows/student/exams/show/components/navbar/ExamMessages.tsx
+++ b/app/javascript/components/workflows/student/exams/show/components/navbar/ExamMessages.tsx
@@ -9,6 +9,7 @@ import Tooltip from '@student/exams/show/components/Tooltip';
 import Icon from '@student/exams/show/components/Icon';
 import NavAccordionItem from '@student/exams/show/components/navbar/NavAccordionItem';
 import { NewMessages, PreviousMessages } from '@hourglass/common/messages';
+import { compact } from '@hourglass/common/helpers';
 import {
   useFragment,
   graphql,
@@ -199,14 +200,17 @@ export const ShowExamMessages: React.FC<{
     `,
     examKey,
   );
+  // We won't wind up in this component unless we have a registration!
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  const myReg = res.myRegistration!;
   useSubscription(useMemo(() => ({
     subscription: messageReceivedSubscriptionSpec,
     variables: {
-      registrationId: res.myRegistration.id,
+      registrationId: myReg.id,
     },
     configs: [{
       type: 'RANGE_ADD',
-      parentID: res.myRegistration.id,
+      parentID: myReg.id,
       connectionInfo: [{
         key: 'ExamMessages_messages',
         rangeBehavior: 'prepend',
@@ -234,61 +238,62 @@ export const ShowExamMessages: React.FC<{
   useSubscription(useMemo(() => ({
     subscription: versionAnnouncementReceivedSpec,
     variables: {
-      examVersionId: res.myRegistration.examVersion.id,
+      examVersionId: myReg.examVersion.id,
     },
     configs: [{
       type: 'RANGE_ADD',
-      parentID: res.myRegistration.examVersion.id,
+      parentID: myReg.examVersion.id,
       connectionInfo: [{
         key: 'ExamMessages_versionAnnouncements',
         rangeBehavior: 'prepend',
       }],
       edgeName: 'versionAnnouncementsEdge',
     }],
-  }), [res.myRegistration.examVersion.id]));
+  }), [myReg.examVersion.id]));
 
   useConditionalSubscription(
     useMemo(() => ({
       subscription: roomAnnouncementReceivedSpec,
       variables: {
-        roomId: res.myRegistration.room?.id,
+        roomId: myReg.room?.id,
       },
       configs: [{
         type: 'RANGE_ADD',
-        parentID: res.myRegistration.room?.id,
+        parentID: myReg.room?.id,
         connectionInfo: [{
           key: 'ExamMessages_roomAnnouncements',
           rangeBehavior: 'prepend',
         }],
         edgeName: 'roomAnnouncementsEdge',
       }],
-    }), [res.myRegistration.room?.id]),
-    !!res.myRegistration.room,
+    }), [myReg.room?.id]),
+    !!myReg.room,
   );
 
-  const personal: ExamMessage[] = res.myRegistration.messages.edges.map(({ node }) => ({
-    type: 'personal',
-    id: node.id,
-    body: node.body,
-    createdAt: DateTime.fromISO(node.createdAt),
+  const personal: ExamMessage[] = compact(myReg.messages.edges?.map((e) => e?.node) ?? [])
+    .map((node) => ({
+      type: 'personal',
+      id: node.id,
+      body: node.body,
+      createdAt: DateTime.fromISO(node.createdAt),
+    }));
+  const roomAnnouncements = compact(myReg.room?.roomAnnouncements.edges?.map((e) => e?.node) ?? []);
+  const room: ExamMessage[] = roomAnnouncements.map((ra) => ({
+    type: 'room',
+    id: ra.id,
+    body: ra.body,
+    createdAt: DateTime.fromISO(ra.createdAt),
   }));
-  const room: ExamMessage[] = res.myRegistration.room?.roomAnnouncements.edges.map(
-    ({ node: ra }) => ({
-      type: 'room',
-      id: ra.id,
-      body: ra.body,
-      createdAt: DateTime.fromISO(ra.createdAt),
-    }),
-  ) ?? [];
-  const version: ExamMessage[] = res.myRegistration.examVersion.versionAnnouncements.edges.map(
-    ({ node: va }) => ({
-      type: 'version',
-      id: va.id,
-      body: va.body,
-      createdAt: DateTime.fromISO(va.createdAt),
-    }),
-  );
-  const exam: ExamMessage[] = res.examAnnouncements.edges.map(({ node: ea }) => ({
+  const versionAnnouncements = compact(myReg.examVersion.versionAnnouncements
+    .edges?.map((e) => e?.node) ?? []);
+  const version: ExamMessage[] = versionAnnouncements.map((va) => ({
+    type: 'version',
+    id: va.id,
+    body: va.body,
+    createdAt: DateTime.fromISO(va.createdAt),
+  }));
+  const examAnnouncements = compact(res.examAnnouncements.edges?.map((e) => e?.node) ?? []);
+  const exam: ExamMessage[] = examAnnouncements.map((ea) => ({
     type: 'exam',
     id: ea.id,
     body: ea.body,
@@ -398,19 +403,18 @@ const ExamMessages: React.FC<ExamMessagesProps> = (props) => {
     `,
     examKey,
   );
-  const dates: DateTime[] = res
-    .examAnnouncements.edges.map(({ node: { createdAt } }) => DateTime.fromISO(createdAt))
-    .concat(
-      res.myRegistration.room?.roomAnnouncements.edges.map(
-         ({ node: { createdAt } }) => DateTime.fromISO(createdAt),
-      ) ?? [],
-    )
-    .concat(
-      res.myRegistration.examVersion.versionAnnouncements.edges.map(
-        ({ node: { createdAt } }) => DateTime.fromISO(createdAt),
-      ),
-    )
-    .concat(res.myRegistration.messages.edges.map(({ node }) => DateTime.fromISO(node.createdAt)));
+  const roomAnnouncements = compact(res.myRegistration?.room?.roomAnnouncements.edges
+    ?.map((e) => e?.node) ?? []);
+  const versionAnnouncements = compact(res.myRegistration?.examVersion.versionAnnouncements
+    .edges?.map((e) => e?.node) ?? []);
+  const personalMessages = compact(res.myRegistration?.messages.edges?.map((e) => e?.node) ?? []);
+  const examAnnouncements = compact(res.examAnnouncements.edges?.map((e) => e?.node) ?? []);
+  const dates = [
+    ...examAnnouncements.map(({ createdAt }) => DateTime.fromISO(createdAt)),
+    ...roomAnnouncements.map(({ createdAt }) => DateTime.fromISO(createdAt)),
+    ...versionAnnouncements.map(({ createdAt }) => DateTime.fromISO(createdAt)),
+    ...personalMessages.map((node) => DateTime.fromISO(node.createdAt)),
+  ];
 
   const anyUnread: boolean = dates.reduce((acc, date) => (acc || date > lastViewed), false);
   const classes = anyUnread ? 'bg-warning text-dark' : undefined;
diff --git a/app/javascript/components/workflows/student/exams/show/components/navbar/Scratch.tsx b/app/javascript/components/workflows/student/exams/show/components/navbar/Scratch.tsx
index 4e27e6fa8..1bf114bb9 100644
--- a/app/javascript/components/workflows/student/exams/show/components/navbar/Scratch.tsx
+++ b/app/javascript/components/workflows/student/exams/show/components/navbar/Scratch.tsx
@@ -18,7 +18,7 @@ const Scratch: React.FC<ScratchProps> = (props) => {
       id="scratchbox"
       value={value}
       onChange={(event): void => {
-        onChange(event.target.value);
+        if (onChange) onChange(event.target.value);
       }}
       as="textarea"
       spellCheck={false}
diff --git a/app/javascript/components/workflows/student/exams/show/containers/navbar/Scratch.ts b/app/javascript/components/workflows/student/exams/show/containers/navbar/Scratch.ts
index eadbee778..246828872 100644
--- a/app/javascript/components/workflows/student/exams/show/containers/navbar/Scratch.ts
+++ b/app/javascript/components/workflows/student/exams/show/containers/navbar/Scratch.ts
@@ -6,7 +6,7 @@ import { updateScratch } from '@student/exams/show/actions';
 const mapStateToProps: MSTP<{
   value: string;
 }> = (state) => ({
-  value: state.contents.answers.scratch ?? '',
+  value: state.contents.answers?.scratch ?? '',
 });
 
 const mapDispatchToProps: MDTP<{
diff --git a/app/javascript/components/workflows/student/exams/show/containers/questions/connectors.ts b/app/javascript/components/workflows/student/exams/show/containers/questions/connectors.ts
index 4b4599a13..4d9255411 100644
--- a/app/javascript/components/workflows/student/exams/show/containers/questions/connectors.ts
+++ b/app/javascript/components/workflows/student/exams/show/containers/questions/connectors.ts
@@ -18,12 +18,12 @@ interface OwnProps {
   bnum: number;
 }
 
-export const isNoAns = (answer: AnswerState): boolean => (
+export const isNoAns = (answer: AnswerState | undefined): boolean => (
   (answer instanceof Object) && (answer as NoAnswerState).NO_ANS
 );
 
 const mapStateToProps: MSTP<{
-  value: AnswerState;
+  value?: AnswerState;
   disabled: boolean;
   locked: boolean;
   examFinished: boolean;
@@ -34,7 +34,7 @@ const mapStateToProps: MSTP<{
   const { status, message } = snapshot;
   const locked = (status === SnapshotStatus.FAILURE);
   const examFinished = (status === SnapshotStatus.FINISHED);
-  const answer = state.contents.answers.answers[qnum][pnum][bnum];
+  const answer = state.contents.answers?.answers[qnum][pnum][bnum];
   return {
     value: isNoAns(answer) ? undefined : answer,
     disabled: locked,
diff --git a/app/javascript/components/workflows/student/exams/show/files.ts b/app/javascript/components/workflows/student/exams/show/files.ts
index 40331ab7a..c39102db9 100644
--- a/app/javascript/components/workflows/student/exams/show/files.ts
+++ b/app/javascript/components/workflows/student/exams/show/files.ts
@@ -20,7 +20,7 @@ export function createMap(files: ExamFile[]): FileMap {
   return ret;
 }
 
-export function firstFile(files: ExamFile[]): ExamFile {
+export function firstFile(files: ExamFile[]): ExamFile | undefined {
   // eslint-disable-next-line no-restricted-syntax
   for (const file of files) {
     if (file.filedir === 'file') {
diff --git a/app/javascript/components/workflows/student/exams/show/helpers.ts b/app/javascript/components/workflows/student/exams/show/helpers.ts
index 6f1d4a6fe..271f7b581 100644
--- a/app/javascript/components/workflows/student/exams/show/helpers.ts
+++ b/app/javascript/components/workflows/student/exams/show/helpers.ts
@@ -1,5 +1,5 @@
 export function getCSRFToken(): string {
-  const elem: HTMLMetaElement = document.querySelector('[name=csrf-token]');
+  const elem: HTMLMetaElement | undefined = document.querySelector('[name=csrf-token]');
   return elem?.content ?? '';
 }
 
@@ -18,6 +18,7 @@ function pulse(elem: HTMLElement): void {
 function scrollToElem(id: string, smooth = true): void {
   setTimeout(() => {
     const elem = document.getElementById(id);
+    if (!elem) return;
     const elemTop = elem.getBoundingClientRect().top + window.pageYOffset;
     window.scrollTo({
       left: 0,
diff --git a/app/javascript/components/workflows/student/exams/show/lockdown/anomaly.ts b/app/javascript/components/workflows/student/exams/show/lockdown/anomaly.ts
index 6bb04456e..5602548a3 100644
--- a/app/javascript/components/workflows/student/exams/show/lockdown/anomaly.ts
+++ b/app/javascript/components/workflows/student/exams/show/lockdown/anomaly.ts
@@ -1,6 +1,11 @@
 import { useEffect, useRef } from 'react';
 import { getCSRFToken } from '@student/exams/show/helpers';
-import { AnomalyDetected, Policy, policyPermits } from '@student/exams/show/types';
+import {
+  AnomalyDetected,
+  AnomalyListener,
+  Policy,
+  policyPermits,
+} from '@student/exams/show/types';
 import { installListeners, removeListeners } from './listeners';
 
 function lockOut(): void {
@@ -40,7 +45,7 @@ export default function useAnomalyListeners(
   policies: readonly Policy[],
   showAlert: (reason: string) => void,
 ): (() => void) {
-  const lst = useRef([]);
+  const lst = useRef<AnomalyListener[]>([]);
   const anomalyDetected: AnomalyDetected = (
     policyPermits(policies, 'MOCK_LOCKDOWN')
       ? showAlert
diff --git a/app/javascript/components/workflows/student/exams/show/reducers/pagination.ts b/app/javascript/components/workflows/student/exams/show/reducers/pagination.ts
index 7bffeabcf..1accc8449 100644
--- a/app/javascript/components/workflows/student/exams/show/reducers/pagination.ts
+++ b/app/javascript/components/workflows/student/exams/show/reducers/pagination.ts
@@ -70,8 +70,8 @@ export default (state: PaginationState = {
         waypointsActive: action.enabled,
       };
     case 'LOAD_EXAM': {
-      const pageCoords = [];
-      const spyCoords = [];
+      const pageCoords: PaginationCoordinates[] = [];
+      const spyCoords: PaginationCoordinates[] = [];
       action.exam.questions.forEach((q, qnum) => {
         const thisQ = {
           question: qnum,
diff --git a/app/javascript/components/workflows/student/registrations/show/DisplayQuestions.tsx b/app/javascript/components/workflows/student/registrations/show/DisplayQuestions.tsx
index 1fa18093e..5c3da3f62 100644
--- a/app/javascript/components/workflows/student/registrations/show/DisplayQuestions.tsx
+++ b/app/javascript/components/workflows/student/registrations/show/DisplayQuestions.tsx
@@ -6,7 +6,7 @@ import { graphql, useFragment } from 'relay-hooks';
 import { DisplayQuestions$key } from './__generated__/DisplayQuestions.graphql';
 
 interface DisplayQuestionsProps {
-  refreshCodeMirrorsDeps: React.DependencyList;
+  refreshCodeMirrorsDeps?: React.DependencyList;
   currentGrading?: CurrentGrading;
   registrationId?: string;
   fullyExpandCode: boolean;
diff --git a/tsconfig.json b/tsconfig.json
index c5b2edf6d..ff1d115d2 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,6 +6,7 @@
     "module": "esnext",
     "moduleResolution": "node",
     "sourceMap": true,
+    "strictNullChecks": true,
     "target": "esnext",
     "jsx": "preserve",
     "allowSyntheticDefaultImports": true,