Cannot log in from UI

[Eyal Lebedinsky]

A friend has a problem where after entering their password it goes back to the login screen.

Looks like gnome-shell is crashing. Looking at syslog I find the following:

Oct  6 16:44:53 ThinkPad-SL510 gnome-shell[2105]: Execution of main.js threw exception: Script <main> threw an exception
Oct  6 16:44:53 ThinkPad-SL510 org.gnome.Shell.desktop[2105]: (EE)
Oct  6 16:44:53 ThinkPad-SL510 org.gnome.Shell.desktop[2105]: Fatal server error:
Oct  6 16:44:53 ThinkPad-SL510 gnome-session[2074]: gnome-session-binary[2074]: WARNING: App 'org.gnome.Shell.desktop' exited with code 1
Oct  6 16:44:53 ThinkPad-SL510 gnome-session-binary[2074]: Unrecoverable failure in required component org.gnome.Shell.desktop
Oct  6 16:44:53 ThinkPad-SL510 gnome-session-binary[2074]: WARNING: App 'org.gnome.Shell.desktop' exited with code 1
Oct  6 16:44:53 ThinkPad-SL510 org.gnome.Shell.desktop[2105]: (EE) failed to read Wayland events: Connection reset by peer
Oct  6 16:44:53 ThinkPad-SL510 org.gnome.Shell.desktop[2105]: (EE)
Oct  6 16:44:53 ThinkPad-SL510 gdm3: GdmDisplay: display lasted 2.384283 seconds

The system was running mostly as originally installed with no significant changes. They are not power users.
No issues of note until recently and they are unaware of any unusual events leading to this situation.

This is 18.04. I did an update/upgrade with no improvement.

As an aside, It was a Wayland system. We started a rescue boot where we did nothing but now the system runs X...

TIA

-- 
Eyal Lebedinsky (eyal at eyal.emu.id.au)