Comment 47 for bug 2003339

I keep having this for weeks now and can confirm the last line before X goes down always is the BadDamage one.
I think it started like 6-8 weeks ago. Once it starts to happen, restarting kwin_x11 mostly won't help for any longer period of time. In the best cases it lasts long enough to allow for a controlled Desktop shutdown, package update and reboot - sometimes not even that. After reboot it keeps going for another 24 to 48 hours before kwin crashes start again. I

I don't think notifications are the one culprit. Yes, notifications sometimes seem to trigger the problem (notably causing latte dock to hang until killed), but not always. Sometimes a mere desktop switch apparently is enough to get it down again. In the worst cases just coming back to the x11 VT (remapping the desktop) did end it. I'll keep re-starting and updating until it gets better since I get it there is a promising patch now. But the general instability really is getting to me :-)
If you want logs of anything you don't already have, drop me a line.
Thanks for looking into this.