If you do an "bildschirmpräsentation" (presentation) or "Bildschirmsperre" (lock screen) it is possible to kill the process because it is not owned by System-user / it is a normal user process.
how to reproduce:
1) start a presentation
2) CTRL-ALT-DEL → taskmngr.exe && kill process ( the taskmanager is always on top)
Or write a batch script which kills the process every 5 seconds
run process as System user