KDE Plasma frequently takes up all system resources leading to crash

Question

I am using Kubuntu (Ubuntu 20.04.4 LTS x86_64) and plasmashell 5.18.8. I have however different problems with it with varying severity.

1. The Task bar freezes
   • I then restart it using quitapp5 plasmashell || killall plasmashell && kstart5 plasmashell
2. The computer is very slow and the mouse only moves several seconds after input
   • I kill plasma using ctl + alt + backspace, since I can not open the terminal in this state
   • Afterwards the computer works again several minutes before becoming slow again. Also the splash screen is shown for far longer than normal.
3. The computer just freezes and is completly unresponsive. I can only turn it off by holding down the power button for 10 seconds.

I also frequenly have the problem that my computer runs out of memory (8 GB + 4 GB swap) and then plasma gets killed automaticially.

I have seen that when the issue nr. 1 occurs, which is about every 30 minutes, that plasma takes over 100% of a CPU kernel and often more than 70% of memory.

When I start plasma it says a lot of stuff about "Invalid Context" and "trying to show an empty dialog", I don't know if that is useful. I can not really find something in journalctl logs after something like this, other then that the computer run out of memory. But I am not a linux pro (yet), so I do not really know what I am looking for.

EDIT Here are the logs from journal ctl when it froze this morning (case 1)

ug 11 09:42:48 caspar-ZenBook-UX334FAC dbus-daemon[781]: [system] Activating service name='org.kde.powerdevil.backlighthelper' requested by ':1.63' (uid=1000 p>
Aug 11 09:42:48 caspar-ZenBook-UX334FAC dbus-daemon[781]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
Aug 11 09:44:32 caspar-ZenBook-UX334FAC wpa_supplicant[820]: wlo1: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-75 noise=9999 txrate=432300
Aug 11 09:44:58 caspar-ZenBook-UX334FAC wpa_supplicant[820]: wlo1: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-76 noise=9999 txrate=432300
Aug 11 09:52:19 caspar-ZenBook-UX334FAC wpa_supplicant[820]: wlo1: WPA: Group rekeying completed with 50:e0:39:62:59:46 [GTK=CCMP]

Answer 1

Doing a full upgrade of the OS and Plasma helped. For doing the update I used the shell accessed with Ctrl + Alt + F2 to ensure that nothing crashes during the update.