Dear Maintainer,

*** Reporter, please consider answering these questions, where appropriate ***

   After usual updating and rebooting, then login I had black or blue window
that said 'you are currently running in fallback mode'. It offered to open
without or with installed add-ons. I tried both options. It just showed this
warning again and again.
   I just pressed the power button. Next time it launched.

Hi Sayat,

sorry for the very late answer. That dialog comes from
cinnamon-launcher: it shows up when the cinnamon process crashes, and
meanwhile metacity is started as a fallback window manager. So during
that boot Cinnamon crashed every time it was restarted, and on the next
boot it worked again.

Without logs from that boot it's not possible to tell what crashed. Has
it happened again since then? If it does, right after the next reboot
please send:

- the file ~/.xsession-errors.old (at each login LightDM moves the log
of the previous session there, so it's lost if you log in more than once
in between)
- the output of: journalctl -b -1 | grep -i -e cinnamon -e segfault

Best regards,
Fabio