I’ve had this happen a couple of times now since upgrading to 18.04: soon (perhaps within a minute) after logging in, Gnome session ends abruptly and I’m thrown back to the login screen. IIRC, in both instances this occurred on the first login after boot, so it does not reoccur on the subsequent re-login, and not on every login (very rarely in fact), and for now I have no better steps to reproduce this other than ”boot, log in”.

Bug #1663839 (reported against 17.04) seems similar, as does bug #1731428 (reported against 17.10).

journalctl output during the issue:

Apr 16 07:00:30 saegusa gnome-session[4342]: gnome-session-binary[4342]: WARNING: Application ’org.gnome.SettingsDaemon.Color.desktop’ failed to register before timeout
Apr 16 07:00:30 saegusa gnome-session-binary[4342]: WARNING: Application ’org.gnome.SettingsDaemon.Color.desktop’ failed to register before timeout
Apr 16 07:00:30 saegusa gnome-session-binary[4342]: Unrecoverable failure in required component org.gnome.SettingsDaemon.Color.desktop
Apr 16 07:00:30 saegusa gnome-session[4342]: gnome-session-binary[4342]: CRITICAL: We failed, but the fail whale is dead. Sorry….
Apr 16 07:00:30 saegusa gnome-session-binary[4342]: CRITICAL: We failed, but the fail whale is dead. Sorry….