I too seem to have this problem. 
Little yellow round exclamation point appears on the item in the DVR Schedule. But the channel guide is fine. And if I go into the guide and select that channel it plays fine.
Plex Media Server Logs_2020-07-22_18-58-22.zip (1.3 MB)
I refreshed the channel guide, re-scanned the channels, and rebooted. None of that helped.
Not sure if it’s coincidence or not, but I noticed it when I started using Plex Media Server as a Service. That’s a whole separate discussion why… Duplicate / multiple servers keep appearing
I haven’t tried to rollback to an older version like @warham30 mentioned.
