Bug 468340

SUMMARY
Plasma desktop seems to stop working after 1 to 6 days of uptime (forcing a reboot)

STEPS TO REPRODUCE
1.  I have not found a pattern that can reproduce the problem.

OBSERVED RESULT
There seem to be different manifestations of the same problem.  I have observed each of the following happening, but not all at once:
1. Patches of the screen go black or are fixed (not updated) with an old image.
2. My Plasma panel stops responding to mouse clicks (and the digital clock on my panel stops updating).
3. All my windows lose their borders.
4. Xorg and sddm use nearly 100% CPU when problem occurs, but not before.

EXPECTED RESULT
None of the above observed results.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 22.04 LTS
KDE Plasma Version: 5.24.7
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.3

ADDITIONAL INFORMATION
I asked the question here
https://askubuntu.com/questions/1458083/desktop-freezing-on-kubuntu-22-04-lts
I followed the suggestions, but they did not work.

I have what appears to be the same problem on four machines, all running Kubuntu 22.04 LTS, two of which are identical models, so I don't think it's a hardware problem.  The models are:
1. Dell Precision 5520 laptop
2. Dell Precision 5530 laptop (x 2)
3. Dell XPS 8940 desktop

Nothing helpful shows up in the logs, and when the problem happens I can `ssh` into the machine or `Alt-Ctrl-F2` to drop to console mode to reboot.

I tried running with a newer kernel (5.19.17 instead of 5.15.0), I tried using Wayland instead of Xorg, but those changes did not prevent the problem.  Before upgrading to Kubuntu 22.04 LTS I ran CentOS 7 (with an older version KDE) on the Precision 5520 for many years with no problems.  So I have at least one stable machine, I've recently switched to using Xfce on the Precision 5520.

I'd be very grateful if someone could suggest things I could do to diagnose what's causing the problem next time it happens.