Quiz block: saving lesson post gets stuck/loop

[katpuumsiili]

1. Add a new lesson
2. Add a Quiz Block to the Gutenberg editor
3. Add the questions and aswers (not necessary)
4. Click Save

--> Save button shows text "Saving...." again and again, but not saving the post/lesson, and loops forever.

PHP / WordPress / Sensei LMS version

PHP 8.3
WP 6.8.3
Sensei LMS 4.25.1
Sensei Pro 1.24.4
Twenty twenty one theme or custom theme, same problem
Plugins ACF + Polylang

Network tab loops request;
post=90908&action=edit&meta-box-loader=1&meta-box-loader-nonce=dd7ajj69b&_locale=user
302

Nothing in the console errors or PHP error log

[donnapep]

Hi @katpuumsiili. Thanks for the report! This issue sounds specific to your WordPress environment.

In the issue description you mention ACF + Polylang. Does this mean that the infinite saving only occurs when both of these plugins are active?

[joashrajin]

@donnapep we have the ticket in 10456981-zd-a8c

The issue was still happening with Sensei LMS + Polylang Pro with the Twenty Twenty One theme. The user seems to have narrowed it down to Polylang. They mentioned "More specifically, the issue doesn’t appear when adding the Quiz block itself, but once a title is added to the first question, the problem begins."

[github-actions]

Support References

This comment is automatically generated. Please do not edit it.

• 10456981-zen

[timopaananen-siili]

Here's more detailed bug report from @katpuumsiili co-worker.

Bug Report: Infinite Save Loop - Sensei LMS + Polylang Pro

Summary

When editing a lesson post type that contains a quiz block (sensei-lms/quiz) and clicking save, the editor enters an infinite save loop. This only occurs when Polylang Pro is active alongside Sensei LMS.

Environment

• WordPress: 6.7.1
• Sensei LMS: 4.24.4
• Polylang Pro: 3.7.2
• PHP: 8.2

Steps to Reproduce

1. Install and activate Sensei LMS and Polylang Pro
2. Create a new Lesson post type
3. Add a Quiz block (wp:sensei-lms/quiz) to the lesson content
4. Add at least one question to the quiz
5. Click "Save" or "Publish"
6. Observe the save indicator looping continuously

Expected Behavior

The lesson should save once and the editor should return to a normal state.

Actual Behavior

The save operation loops infinitely, making repeated POST requests to:

• wp-json/wp/v2/lessons/{id}
• wp-json/sensei-internal/v1/lesson-quiz/{id}

The browser's Network tab shows continuous requests until the browser is force-closed.

Root Cause Analysis

The issue is a browser-level request loop (not PHP recursion):

1. User clicks Save
    ↓
2. Gutenberg → PUT /wp/v2/lessons/{id}
    ↓
3. Sensei → POST /sensei-internal/v1/lesson-quiz/{id}
    ↓
4. Polylang modifies REST response (adds lang/translations fields)
    ↓
5. Gutenberg compares response to saved state
    ↓
6. Gutenberg sees "unexpected" fields → marks post as "dirty"
    ↓
7. Gutenberg auto-saves → Back to step 2
    ↓
8. INFINITE LOOP

The Core Problem

When Sensei saves quiz data via its internal REST API endpoint (/sensei-internal/v1/lesson-quiz/{id}), Polylang Pro intercepts the response and adds language/translation metadata. Gutenberg's dirty-state detection interprets these additional fields as "unsaved changes" and triggers another save.

The quiz post type in Sensei is tied 1:1 to lessons and should not be independently translatable, but Polylang still processes its REST responses.

Recommended Fix for Sensei LMS

Option 1: Mark Internal API Responses

Add a header or response flag that other plugins can check:

// In Sensei's REST API controller
$response->header( 'X-Sensei-Internal', 'true' );

Other plugins like Polylang could then check:

if ( $response->get_headers()['X-Sensei-Internal'] ?? false ) {
    return $response; // Don't modify internal responses
}

Option 2: Use Private Endpoint Pattern

Consider using an underscored route pattern that is conventionally treated as private:

// Instead of: /sensei-internal/v1/lesson-quiz/{id}
// Use: /_sensei/v1/lesson-quiz/{id}

Option 3: Bypass REST API for Quiz Saves

Since quizzes are internal to lessons, save quiz data directly without triggering the REST response chain:

// Direct update instead of REST endpoint
wp_update_post( $quiz_data );
update_post_meta( $quiz_id, '_quiz_data', $quiz_meta );
// No REST response for Polylang to intercept

Impact

• Affected: Lesson editing with Quiz blocks when both plugins are active
• Not Affected: Other post types, lessons without quizzes, standard WordPress content

Workaround

We have implemented a site-specific workaround that:

1. Disables Polylang's REST processing for Sensei-specific routes
2. Removes the quiz post type from Polylang's translatable types
3. Blocks duplicate REST requests within a time window
4. Adds client-side save throttling as backup protection

This workaround is functional but should not be necessary if either plugin implements proper endpoint isolation.

---

Report Created: December 2025
Tested With: WordPress 6.7.1, Sensei LMS 4.24.4, Polylang Pro 3.7.2, PHP 8.2