Comment 6 for bug 1776002

This sounds like bug 1766137 and the secondary bug mentioned within that. It was fixed for 18.04 only 14 hours ago (https://launchpad.net/ubuntu/+source/gdm3/3.28.2-0ubuntu1.2)

Please update your system and retest. If the problem persists then please run:

  dpkg -l > dpkg.txt

and send us the resulting dpkg.txt