I believe the issue is that the gnome-session-inhibit call is terminated after the upgrade unless you are running a GNOME session.
https://bazaar.launchpad.net/~ubuntu-core-dev/ubuntu-release-upgrader/trunk/view/head:/DistUpgrade/DistUpgradeQuirks.py#L444
After the upgrade completed and choosing not to reboot I was presented with a lock screen that continually said "Authentication failed".
Did your upgrade complete and then the screen locked?
I believe the issue is that the gnome-session- inhibit call is terminated after the upgrade unless you are running a GNOME session.
https:/ /bazaar. launchpad. net/~ubuntu- core-dev/ ubuntu- release- upgrader/ trunk/view/ head:/DistUpgra de/DistUpgradeQ uirks.py# L444
After the upgrade completed and choosing not to reboot I was presented with a lock screen that continually said "Authentication failed".
Did your upgrade complete and then the screen locked?