For about 2 weeks now (I have no idea what triggered the change though) my Xubuntu 16.04 system doesn't do anything when i press the shutdown button (via the whisker menu->logout->shutdown), except for closing my Seafile main window. All other windows and applications (including the Seafile in the tray) continue to function like normal. Only after pressing shutdown again does the system proceed with a regular shutdown.
I assume no-one knows what causes this strange behaviour or how to fix it. How can I debug this? I don't see anything suspicious in the syslog nor dmesg.
UPDATE: now when I try to log out a second time, it fails as well but now a message
Received error while trying to log out: Session manager must be in idle state when requesting a shutdown
sudo shutdown -h now?