I seem to have the following bug on Plex for Apple TV.
Collections with the same name in different libraries e.g. movies and TV shows are not listed in the collections detail page in the various collections.
For example, the “movie” collection only shows the items in the movie collection, but not the TV Show items as described under the “Collections Detail Page” heading in https://support.plex.tv/articles/201273953-collections/
It is working 100% on the Plex web interface as well as Plex for iOS. It only seems to be a bug in Plex for Apple TV