Comment 86 for bug 1733557

count me an additional sufferer - 16.04.4, upgraded as upgrades came out. I also see the behavior go away for a time, then come back after the computer has not rebooted for a period of time. I see it no matter how the computer is locked: crtl-alt-L, lid close to sleep, timeout, the . Once the authentication error shows up, it doesn't go away until a full reboot. Single user/session

Dell XPS 15 (9550) intel/nvidia, stock everything, except kernel updated to 4.15.0-20-generic #21~16.04.1-Ubuntu