wp-remove-post-lock/releaseLock

I’ve encountered this issue with several WordPress installations.

The problem seems to be caused by various plugins and/or themes such as the Polylang plugin and the Divi theme. In my search for a fix I never needed to look outside the core WP4.4 code, though, so more likely it’s not.

The problem is as such:

1. Go to the pages.

2. Click on the title of a page or on any other link to start editing the page.

3. Javascript file wp-admin/js/post.min.js now fires off a POST to wp-admin\admin-ajax.php with action wp-remove-post-lock.
This request runs for as long as PHP allows, I tried upto 300 seconds.
It doesn’t return anything, instead ends in an error.
After the error (so after a ~300 seconds wait, since it’s a blocking call), the page finally changes to the new URL for the edit page.

I “solved” this by setting releaseLock in post.js (and it’s equivalent in post.min.js to false by default. There does not seem to be a clean fix for this.

Does anybody know what could be causing this and how to properly fix it?

[ No bumping please. ]