beta version (5.1.1130.26)

[QZMTCH]

I'm also on version 102 and haven't noticed any major issues. If a particular extension stops working, I revert back to one of the previous versions that worked. So far, I haven't had any display issues with sites – at most I couldn't access some of them, but that was fixed by switching the user agent.
Maybe we're just talking about different things. I don't dispute that something can break, or work incorrectly. But I don't see why I should keep updating my browser or extensions, if everything works fine on previous versions.
Updating CSS rules can cause old websites that haven't been updated for a while to display incorrectly. I don't know any specific examples, but it's possible that it could happen. There's no way to tell for sure, but I can't see any reason why it wouldn't be possible in theory. There doesn't seem to be a middle ground here.

For example, a page https://market.yandex.ru/catalog--med-i-...?hid=91345 looks like this on engine 102 https://i.imgur.com/980oDAH.png and so on 118 https://i.imgur.com/Kbjp6MB.png 
if you don't see problems, it doesn't mean they don't exist

PS https://webextension.org/listing/gmail-notifier.html and about extensions, this does not work on old engines, but what does work (previous versions) their functions no longer work mark as read