In T233127#5563134, @mobrovac wrote:

Update: I think I found the bug in RESTBase. I deployed the fix yesterday and so far so good. I will leave RB logging on until Monday to make sure the problem is indeed fixed.

In the meantime, I also found how to reproduce the bug, so if there are any testers willing to try it, feel free to test it out. The bug essentially happens on a first VE-edit of a page (that is, open the browser, load a page, click on edit) for pages that have been last edited more than 24h prior.

Is there any debugging tool that can be activated and can record all client/server swingers data in case of hitting the error?

It is evident the bug has not been fixed, it has only decreased frequency.

I no longer observed that bug after they (developers) claimed to have fixed it, but if it still persists today evidently the underlying problem remains.

The problem I reported still go on, on random pages, and is not reproducible. The only workaround I found to don't lose job until then, is to copy and paste into a new window that NOT recovers the unsaved work (because otherwise it doesn't save it again with the same error message).

Try to made more deleting lines and modify wikilink. The problem cannot reproduce at every single edit, but it appears very frequently.