Since I have updated the OS to Sierra, I'm facing several issue (one example: Character Accent Menu doesn't appear anymore in macOS Sierra)
Another bothering issue that is, I just can't log out. If I try to log out, shut down or restart the device, my applications are getting closed, the status and dock bars disappear, then... nothing. Just the desktop's background and my mouse. Can't do anything except moving the house, can't open Finder anymore, etc... The only way is to do a long press on the power button.
If I log as a guest user, this problem does not occur. So, like my keyboard's issue, it has something to do with some broken plist, preferences...
Anyway to trackdown what is causing that?