I have a client with a site getting the annoying “**another update is currently in progress**” error when trying to update core WordPress. I manually updated overwriting the files, and tried doing a reinstall after the site was fully updated, and it still gets that error.
There is no reference to core\_updater.lock in the database, or anything along that line at all.
The popular plugin for this says there are no blocks, and to proceed with the updates.
Plugins update fine.
The issue still happens with all plugins deactivated.
I have not tried using a stock theme, but I don’t know that the theme should have any effect on that (correct me if I’m wrong). They’re using an Avada child theme, which is fully updated, and the patcher also worked fine.
Myself, with what you describe, here is what I would do:
Temp debug the `create_lock` function inside of `wp-admin/includes/class-wp-upgrader.php`
Have it open and write to a temp file then write out to it the values of things along the ways to a `return false` to see which one is returning false (and thus triggering the message), then from there debug further.