Course Presentation content upgrade stops with 404 after upgrading hundreds of items (WordPress H5P 1.17.9)

Hello,

I am using H5P on WordPress and I am trying to upgrade my existing H5P content to the latest library version.

My H5P libraries were upgraded successfully. After that, I started the "Upgrade content" process for existing content.

The upgrade works correctly for a large number of Course Presentation contents (more than 200 items are upgraded successfully).

However, after some time, the upgrade process stops and the browser console shows an XHR error:

POST:

admin-ajax.php?action=h5p_content_upgrade_progress&id=239

Status:

404 Not Found

The response is not a JSON error message. It is the normal WordPress 404 HTML page.

Important observations:

- admin-ajax.php itself works correctly.

- The upgrade process can continue after I manually open the problematic Course Presentation and click "Save".

- After saving that content manually, the upgrade continues and then stops again at another Course Presentation.

- There are still around 360 Course Presentation contents that need to be upgraded.

- This suggests that some older Course Presentation contents contain data that cannot be automatically migrated until they are re-saved.

Environment:

- WordPress: 7.0.2

- H5P plugin: 1.17.9

- Content type: Course Presentation

- Browser: Chrome

I would like to know:

1. Is there a known issue with Course Presentation content upgrades where old content needs to be manually saved before migration?

2. Is there a recommended way to batch re-save or migrate old Course Presentation contents?

3. Could this be related to a specific Course Presentation library version or an upgrade script (upgrades.js)?

I can provide an exported .h5p file from one of the problematic presentations if needed.

Thank you!