Yep, same issue here, and it's very frustrating, as is having all my Favorites suddenly vanish! Forcing me to have one-by-one, re-register every channel that had been in the list. Plus, the Recents list is never, ever accurate!
Yes, I have noticed that favorites tend to drop from the list as well as channels just being auto hid or unhidden. And no, the Recents never populate in the list for me either. As I mentioned in another post I never really use favorites anyway though.
The main issue I have with favorites is that the category doesn't lock. So when you pull up the guide again you are automatically viewing all channels. So you have to go to favorites and search from the beginning of your list instead of starting at the channel you are on. Not a big problem if you only have 10 or so channels as favorites I guess. I have 120-150 or so and many happen to be in clusters. I would love to have Roku's Channel menu structured like the Plex app. It has the same categories that Roku does and several more. However if you choose favorites, it locks your choice and a big bonus is being able to move channels in the order you choose within favorites. That change is on my Christmas wish list. 😁
