Created attachment 117107 [details] screenshot To reproduce just hover over the entry of some app in the task manager a few times. At some point the thumbnail will turn black like we can see in my screenshot SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 5.14.4 Qt Version: 5.12.0 KDE Frameworks Version: 5.53.0
Are you still able to reproduce this? I cannot.
This problem has not occurred for a long time on my system.
Great, let's call it fixed. :)