I think the problems may have different root causes. I think with my series content problem, there's some kind of "oldest not viewed". When I subscribed to a new program, it worked correctly. When I subscribe to an existing program, the oldest not viewed can be months or years in the past, and it may not be available on any Roku source. So, stuck with a "clear queue" or "mark all read" feature.
I wonder in your case if there's something about formats, like maybe standard def became available for free but your settings only show you HD or 4K content. Can you fish around and see if there are different formats (heck, even different language versions) that might account for it?