Switching User back from Root ends in black screen and unresponsive system

Hi, i’m not sure if this might be a bug.

Yesterday i switched form my standard user to root and back again to the standard user.
Unfortunately this ended with a black screen and an unresponsive system. So i needed to shutdown my PC manually.

Is a back and forth switch between standard user and root not apropriate in Linux? Perhaps i needed to log off and on instead?

Or is it perhaps a bug of KDE Plasma?