Hey there!
I've been using YouTube on AndroidTV (via Nexus Player) to watch tons of content without having to go through the hassle of pulling it up on my phone and using chromecast to watch on TV. Two channels I watch often are KhanAcademyMedicine and Mobility WOD. Each has 300+ videos and many playlists. However, I guess there was some kind of update to the app for androidTV because now it only allows you to scroll through 12 videos (or 12 playlists) total. Not at a time, total. This means if I go to their channels there is no way for me to browse to find the video I want to watch, unless it happens to be one of the 12 out of the 300+ videos they have.
I'm assuming this happened because there was an update. Is there any way to undo this? The list of videos used to just go and go and go.
You can always download the old YouTube apk from apkmirrors and install it.