SUMMARY
...where it is generally responding (like the app launcher can be triggered, widgets like clock are responding) but:
- new started apps don't show up on the task manager
- enabling Bluetooth hides it from the "arrow menu" but it doesn't show up in the system tray (other icons with similar behavior are probably affected too)
- (sometimes) is flashing 
- apps minimized in the notification tray(?) like qBittorrent or Elisa cannot be triggered

This happens after some time it's running or is idle with locked screen.