In T348797#9322204, @ngkountas wrote:

One last question: have you noticed that the issue is happening for all translations or it only happens when translating some articles that meet specific criteria?

I managed to translate several articles without getting this error, even before it was reported that there were fixes that were supposed to fix the error. But these articles did not differ in anything special.

Here's another screenshot of the errors and warnings after (another) translation autosave freezes: http://prntscr.com/d-LVtSfarqoB

A screenshot of the translation autosave hanging: http://prntscr.com/urRIu1qVMuTi

"Did you translated a lot of sections/paragraphs in a row by clicking on the placeholder section?" - yes.

Problem is NOT resolved. Just tried to translate the article https://en.wikipedia.org/wiki/AIM_(software) - part of the translation was not preserved (see: https://uk.wikipedia.org/wiki/%D0%A1%D0%BF%D0%B5%D1%86%D1%96%D0%B0%D0%BB%D1%8C%D0%BD%D0%B0:%D0%9F%D0%B5%D1%80%D0%B5%D0%BA%D0%BB%D0%B0%D0%B4_%D0%B2%D0%BC%D1%96%D1%81%D1%82%D1%83#draft (the full URL doesn't work here for some reason)). Autosave froze somewhere after half of the article had been translated.

No, the problem has not disappeared.

After trying to complete the translation, it stopped loading altogether: http://prntscr.com/tVk23A2ET_t_
URL: https://uk.wikipedia.org/w/index.php?title=%D0%A1%D0%BF%D0%B5%D1%86%D1%96%D0%B0%D0%BB%D1%8C%D0%BD%D0%B0:%D0%9F%D0%B5%D1%80%D0%B5%D0%BA%D0%BB%D0%B0%D0%B4_%D0%B2%D0%BC%D1%96%D1%81%D1%82%D1%83&campaign=contributionsmenu&from=ru&page=%D0%9A%D0%BE%D0%BD%D1%82%D0%B0%D0%BA%D1%82%D1%8B+Windows&targettitle=%D0%9A%D0%BE%D0%BD%D1%82%D0%B0%D0%BA%D1%82%D0%B8+Windows&to=uk

I confirm the problem.
OS: Windows 8.1 x64.
Browser: Mozilla Firefox 115.3.1esr x64.
Translated article: https://ru.wikipedia.org/wiki/%D0%9A%D0%BE%D0%BD%D1%82%D0%B0%D0%BA%D1%82
The preserved article: https://uk.wikipedia.org/w/index.php?title=%D0%A1%D0%BF%D0%B5%D1%86%D1%96%D0%B0%D0%BB%D1%8C%D0%BD%D0%B0:%D0%9F%D0%B5%D1%80%D0%B5%D0%BA%D0%BB%D0%B0%D0%B4_%D0%B2%D0%BC%D1%96%D1%81%D1%82%D1%83&campaign=contributionsmenu&from=ru&page=%D0%9A%D0%BE%D0%BD%D1%82%D0%B0%D0%BA%D1%82%D1%8B+Windows&targettitle=%D0%9A%D0%BE%D0%BD%D1%82%D0%B0%D0%BA%D1%82%D0%B8+Windows&to=uk&revision=124585601 (the article was translated in its entirety)
Screenshot: http://prntscr.com/-MHQTkpPbye9
My post on MediaWiki: https://www.mediawiki.org/w/index.php?title=Topic:Xrdi08uqph6m8y6g&topic_showPostId=xrmi0b2swfwhym0z#flow-post-xrmi0b2swfwhym0z