@YouTubeTV when are y'all looking to add the feature to Mark an episode viewed. We run into the issue all the time not knowing what episode we have watched. Most of the time after watching an episode it shows we haven't watched it.
Regarding the issue with the "watched" tag on an episode, please try restarting your device and the watch status on the shows should update. Please let us know if that doesn't fix it. (2/2)