diff --git a/ProcessMaker/Helpers/ScreenTemplateHelper.php b/ProcessMaker/Helpers/ScreenTemplateHelper.php
index 67a3684c3f..b6af576270 100644
--- a/ProcessMaker/Helpers/ScreenTemplateHelper.php
+++ b/ProcessMaker/Helpers/ScreenTemplateHelper.php
@@ -4,6 +4,32 @@
 
 class ScreenTemplateHelper
 {
+    private const RENDERABLE_STRING_FIELDS = [
+        'ariaLabel',
+        'content',
+        'fieldValue',
+        'helper',
+        'label',
+        'loadingLabel',
+        'placeholder',
+    ];
+
+    /**
+     * Remove serialized Vue component definitions from screen config.
+     *
+     * Screen templates can contain old inspector metadata where inspector.type
+     * is a serialized Vue component object. That data is not needed at runtime
+     * and can reach renderer paths that expect Mustache templates to be strings.
+     */
+    public static function sanitizeScreenConfig($config): array
+    {
+        if (!is_array($config)) {
+            return [];
+        }
+
+        return self::sanitizeConfigValue($config);
+    }
+
     /**
      * Remove screen components from the configuration based on the provided components.
      *
@@ -402,4 +428,65 @@ public static function generateCss($cssArray)
 
         return $cssString;
     }
+
+    private static function sanitizeConfigValue($value, ?string $key = null)
+    {
+        if ($key === 'validation' && is_array($value) && $value === []) {
+            return null;
+        }
+
+        if (in_array($key, self::RENDERABLE_STRING_FIELDS, true)) {
+            return self::sanitizeRenderableString($value);
+        }
+
+        if (!is_array($value)) {
+            return $value;
+        }
+
+        if (array_is_list($value)) {
+            return array_map(fn ($item) => self::sanitizeConfigValue($item), $value);
+        }
+
+        $sanitized = [];
+        foreach ($value as $childKey => $childValue) {
+            if ($childKey === 'inspector' && is_array($childValue)) {
+                $sanitized[$childKey] = array_map(
+                    fn ($item) => self::sanitizeInspectorItem($item),
+                    $childValue
+                );
+                continue;
+            }
+
+            $sanitized[$childKey] = self::sanitizeConfigValue($childValue, (string) $childKey);
+        }
+
+        return $sanitized;
+    }
+
+    private static function sanitizeInspectorItem($item)
+    {
+        if (!is_array($item)) {
+            return $item;
+        }
+
+        $sanitized = [];
+        foreach ($item as $key => $value) {
+            if ($key === 'type' && is_array($value)) {
+                continue;
+            }
+
+            $sanitized[$key] = self::sanitizeConfigValue($value, (string) $key);
+        }
+
+        return $sanitized;
+    }
+
+    private static function sanitizeRenderableString($value): ?string
+    {
+        if ($value === null || is_array($value)) {
+            return null;
+        }
+
+        return is_string($value) ? $value : (string) $value;
+    }
 }
diff --git a/ProcessMaker/Templates/ScreenTemplate.php b/ProcessMaker/Templates/ScreenTemplate.php
index 742cd5048d..964eb303eb 100644
--- a/ProcessMaker/Templates/ScreenTemplate.php
+++ b/ProcessMaker/Templates/ScreenTemplate.php
@@ -854,8 +854,11 @@ private function mergeFields($screen, $currentScreenPage, $newTemplateScreen, $t
                 throw new MissingScreenPageException();
             }
 
-            $templateComponents = ScreenTemplateHelper::getScreenComponents($newTemplateScreen->config,
-                $supportedComponents, false)[0]['items'];
+            // Sanitize only imported template components so existing screen config is not altered.
+            $templateComponents = ScreenTemplateHelper::sanitizeScreenConfig(
+                ScreenTemplateHelper::getScreenComponents($newTemplateScreen->config,
+                    $supportedComponents, false)[0]['items'] ?? []
+            );
 
             $screenConfig[$currentScreenPage]['items'] =
                 array_merge($screenConfig[$currentScreenPage]['items'], $templateComponents);
@@ -866,11 +869,14 @@ private function mergeFields($screen, $currentScreenPage, $newTemplateScreen, $t
 
     private function getTemplateComponents($newTemplateScreen, $templateOptions, $supportedComponents)
     {
-        return !in_array('Fields', $templateOptions)
+        $templateComponents = !in_array('Fields', $templateOptions)
             ? ScreenTemplateHelper::getScreenComponents($newTemplateScreen->config,
                 $supportedComponents, false)[0]['items']
             ?? []
                 : $newTemplateScreen->config[0]['items'] ?? [];
+
+        // Sanitize only imported template components so existing screen config is not altered.
+        return ScreenTemplateHelper::sanitizeScreenConfig($templateComponents);
     }
 
     private function setScreenConfig($screen)
diff --git a/tests/Feature/Templates/Api/ScreenTemplateTest.php b/tests/Feature/Templates/Api/ScreenTemplateTest.php
index 36e684888d..08cc543e05 100644
--- a/tests/Feature/Templates/Api/ScreenTemplateTest.php
+++ b/tests/Feature/Templates/Api/ScreenTemplateTest.php
@@ -392,13 +392,11 @@ public function testSharedTemplateAuthorization()
 
     public function testApplyCssToExistingScreen()
     {
-        // Create a new screen with two pages and no custom_css
-        $screenPath = base_path(self::SCREEN_PATH);
-        $screenData = json_decode(File::get($screenPath), true);
-
+        // Create a new screen with no config and no custom_css
         $screen = Screen::factory()->create([
-            'config' => $screenData,
+            'config' => null,
         ]);
+        $this->assertNull($screen->config);
         $this->assertNull($screen->custom_css);
 
         // Create a screen template with custom_css
@@ -420,13 +418,14 @@ public function testApplyCssToExistingScreen()
         $response->assertStatus(200);
 
         if (class_exists(VersionHistory::class)) {
-            $updatedScreen = \ProcessMaker\Models\ScreenVersion::select('custom_css')->where('screen_id', $screen->id)->latest()->firstOrFail();
+            $updatedScreen = \ProcessMaker\Models\ScreenVersion::select('config', 'custom_css')->where('screen_id', $screen->id)->latest()->firstOrFail();
         } else {
-            $updatedScreen = Screen::select('custom_css')->where('id', $screen->id)->firstOrFail();
+            $updatedScreen = Screen::select('config', 'custom_css')->where('id', $screen->id)->firstOrFail();
         }
 
         // Check that the screen has the custom_css
         $this->assertNotNull($updatedScreen->custom_css);
+        $this->assertNull($updatedScreen->config);
     }
 
     public function testApplyFieldsToExistingScreen()
@@ -475,6 +474,43 @@ public function testApplyFieldsToExistingScreen()
 
         // Check that the screen config is not empty
         $this->assertNotEmpty($updatedScreen->config[1]['items']);
+        $this->assertScreenConfigSanitized($updatedScreen->config);
+    }
+
+    public function testApplyTemplateSanitizesSerializedInspectorComponents()
+    {
+        $templatePath = base_path(self::SCREEN_TEMPLATE_PATH);
+        $screenTemplateData = File::get($templatePath);
+
+        $screenTemplate = $this->createScreenTemplateFromManifest($screenTemplateData);
+
+        $screenPath = base_path(self::SCREEN_PATH);
+        $screenData = json_decode(File::get($screenPath), true);
+
+        $newScreen = Screen::factory()->create([
+            'config' => $screenData,
+        ]);
+
+        $route = route('api.template.applyTemplate', [
+            'type' => 'screen',
+            'id' => $screenTemplate->id,
+        ]);
+
+        $response = $this->apiCall('POST', $route, [
+            'screenId' => $newScreen->id,
+            'templateOptions' => ['Fields', 'Layout'],
+            'currentScreenPage' => 1,
+        ]);
+
+        $response->assertStatus(200);
+
+        if (class_exists(VersionHistory::class)) {
+            $updatedScreen = \ProcessMaker\Models\ScreenVersion::select('config')->where('screen_id', $newScreen->id)->latest()->firstOrFail();
+        } else {
+            $updatedScreen = Screen::select('config')->where('id', $newScreen->id)->firstOrFail();
+        }
+
+        $this->assertScreenConfigSanitized($updatedScreen->config);
     }
 
     public function testApplyLayoutToExistingScreen()
@@ -574,4 +610,74 @@ public function testApplyFullTemplateToExistingScreen()
         // Check that the screen has the custom_css
         $this->assertNotNull($updatedScreen->custom_css);
     }
+
+    private function assertScreenConfigSanitized(array $config): void
+    {
+        foreach ($config as $page) {
+            $this->assertScreenConfigValueSanitized($page);
+        }
+    }
+
+    private function createScreenTemplateFromManifest(string $manifest): ScreenTemplates
+    {
+        $screenTemplate = ScreenTemplates::make([
+            'unique_template_id' => 'serialized-inspector-regression',
+            'name' => 'Serialized Inspector Regression',
+            'description' => 'Template with serialized Vue component inspector metadata.',
+            'version' => '1.0.0',
+            'user_id' => null,
+            'editing_screen_uuid' => null,
+            'screen_category_id' => ScreenCategory::factory()->create()->getKey(),
+            'screen_type' => 'FORM',
+            'media_collection' => 'serialized-inspector-regression-media',
+            'manifest' => $manifest,
+            'screen_custom_css' => null,
+            'is_public' => true,
+            'is_default_template' => false,
+            'is_system' => false,
+            'asset_type' => null,
+        ]);
+        $screenTemplate->saveOrFail();
+
+        return $screenTemplate;
+    }
+
+    private function assertScreenConfigValueSanitized($value): void
+    {
+        if (!is_array($value)) {
+            return;
+        }
+
+        if (array_key_exists('inspector', $value) && is_array($value['inspector'])) {
+            foreach ($value['inspector'] as $inspector) {
+                if (is_array($inspector) && array_key_exists('type', $inspector)) {
+                    $this->assertFalse(is_array($inspector['type']));
+                }
+            }
+        }
+
+        foreach (['content', 'label'] as $field) {
+            if (!array_key_exists($field, $value)) {
+                continue;
+            }
+
+            $this->assertFalse(is_array($value[$field]));
+        }
+
+        if (
+            array_key_exists('tooltip', $value)
+            && is_array($value['tooltip'])
+            && array_key_exists('content', $value['tooltip'])
+        ) {
+            $this->assertFalse(is_array($value['tooltip']['content']));
+        }
+
+        if (array_key_exists('validation', $value) && is_array($value['validation'])) {
+            $this->assertNotEmpty($value['validation']);
+        }
+
+        foreach ($value as $childValue) {
+            $this->assertScreenConfigValueSanitized($childValue);
+        }
+    }
 }