I have enabled automatic tracking. Worked for some hours. Then I locked the screen and went for lunch. When I came back the screen locker was unresponsive and didn't show the password prompt. After unlocking the session via the command line, I could see that KTimeTracker had opened about 620 message boxes telling me that the desktop session was idle since whatever and whether I wanted to continue. The system reacted extremely slow, so that quickly closing the 600+ message boxes wasn't an option. Even terminating the session via the command line and logging in again didn't recover the session, so that I resorted to a reboot. I have uninstalled KTimeTracker again. I anyway need time tracking by virtual desktop and not by application window which KTimeTracker doesn't provide.
Same thing here. The freeze is caused by kwin handling the windows too slowly, which I solved by patching kwin. It is still rogue behaviour by ktimetracker.