We are in the process of migrating users from 1809 LTSC images/pools to 20H2 SAC with AppVolumes 4 . Both old and new are using NVidia GRID, the same profile across the board. Horizon servers are at 7.13.1 and agents on both images are 7.13. What we are seeing for some users is that when they start their session, they get to the desktop and then within a minute screens start flickering but it's like one goes down then up and then the other one does that and then again and again. In some cases only one screen comes up and no other screen. In both cases either rebooting client or physically disconnecting monitor and plugin it back in resolves the issue without logging off from the session. So far we see that happening on Dell Wyse P25 and 10zig 5948 thinclients. ALso the same issue shows up on both blast and pcoip. THe issue wasnt' present before on LTSC and we are not really sure why it comes up on SAC now. Another problem we have noticed is that if user has 3 screens with one being vertical, a user will never be able to log in. The session is started but the user only sees black screens and getting kicked back to sing in page. This particular issue is very reproducible on Dell P45 or Dell P25 clients. When orientation is horizontal on all screens then everything works.
Anyway, the main problem now are the flickering screens. For now users simply reboot their clients and reconnect to session and all is good for the rest of the day.
Don't know why all of the sudden we are seeing so many Display issues on SAC with the same agents.
Any input would be greatly appreciated