Created attachment 110101 [details] demonstration My screenshot shows the issue.
I see it too sometimes, mostly for root processes.
FWIW: Seeing this in OpenMandriva Lx as well. Also Plasma 5.19.90.
This could be closed since KSysGuard has been replaced with Plasma System Monitor.
Is System Activity (ctrl+esc) part of ksysguard? It is affected by this bug too.
ksysguard is no longer maintained, in Plasma 6 there is the Plasma system monitor for this task. If your issue still happens with the Plasma 6 replacement, please re-open and we can move this bug to the new product, thanks!