Saving Impossible And No Error/Warning Message Whatsoever in Case Of Edit Conflict

I'm using the latest LTS release.

Today we had the problem that a user could not save an article at all, but got no feedback whatsoever from Xwiki - the page just stayed in edit mode.

It turned out this was a concurrent edit:

1. First of all, it's too easy to enter a concurrent edit situation. If you edit an article with one account, wait a while (not even too long, I think I waited about 1 hour during my test, maybe even shorter) and then try to edit it with a second session, you can do so without any warning.
2. Second, if the first user then wants to save, it won't work if there are merge conflicts, and there is no feedback in any way that something went wrong. Very bad usability.

See the attached screen recording for a demonstration. You're seeing the older session which was "overtaken" by a concurrent edit session (in which the concurrently editing using was never warned that there already was another session in progress in the first place) and then tries to save.

You can see the page silently stays in edit mode, can't be saved, editing can't be cancelled using the button, and after a browser-triggered reload (F5), the new content appears and all edits are lost.