SDDM crashes resuming from Sleep?

[Snowhog]

I assume that is what's happening. I put the PC to Sleep, sometimes with Firefox open; most of the time with any running application closed. When I have the PC resume from Sleep; pressing any key; sometimes all I get is a black screen with a functioning mouse; the cursor moves. This happens several times a month.

I reboot using the Magic Key Sequence: Alt+Prnt+REISUB; and I am able to log in just fine. How can I diagnose this? Is SDDM actually crashing? Can I do something to restart it without having to do the clean process shutdown and reboot?

[die.boer]

when it happens again ,after reboot check logs

journalctl -b -1 -p 3

Look for:GPU errors , kwin crashes , segfaults

also , to see if it is actually SDDM...when it happens again,switch to TTY
If you get a login prompt,your system is alive...not SDDM
If TTY is also dead...deeper kernel/GPU issue

[die.boer]

Try recovering without reboot
When it happens: Restart your graphical session (not full reboot)
From TTY:

systemctl restart display-manager

This restarts SDDM, logging you out but avoiding a full reboot.