TLDR: Disabled cloud save synchronization for supported games option in Ubisoft Connect - no more crashes.
So I started playing AC Valhalla around 16 of January. Every 1-5 hours I had random Blue Screen Event (Live Kernel 141) mostly with windows reboot. I had 18 in game hours and 6 Blue Screen events.
I panicked and started benchmarking and stress testing my PC with everything: RelalBench - stress test, 3D Mark - GPU stress test, memtest etc - and there was no instability, no crashes, everything was fine.
Checked integrity of files multiple times, installed new nvidia drives many times (461.40), windows up to date...
And AC Valhalla is not very demanding game when compared to for example Cyberpunk - in which I spent over 200hrs with no crash.
Than I noticed that all of these 141Live Kerenel events had something in common - some type of memory access violation usually marked with code 0000005. Also Ive seen here on forums that many people blame stability issues on Ubisoft Connect.
So i disabled cloud save synchronization for supported games and havent encountered a single crash while playing Valhalla since then. Spent around 30 more hours over last 4 days without single crash.
My theory is that there is some confilct beetwenn Ubisof Connact, AC Valhalla and Windows when it comes to saving/synchronizing. Weird thing is that even tough the game is uploading saves to cloud while playing, Ubisoft Connect is synchronizing them agaain right after exiting game.
Another weird thing is that my Ubisoft Connect is not updating at all. Last update was on 18 of January and there was no update since then, even tough I see in news feed that there was more updates in last weeks.
Is there any "check for updates button" in Ubisoft Connect?
That might be also the culprit but Im too afraid now to reinstall Ubisoft Connect, beacuse I dont want to destablilze my game again since changing one option in Ubisoft Connect resolved issue.