I have a huge movie library, divided by categories. Plex on ios (ipad) Android (tablette) and my roku shows complete movie library (action-crime) (adventure-comedy) etc. but in the windows 10 app it only shows about half the library.
I think we need a bit more info - define huge library. What machine is the app running on - have you set any particular filters - did you give it time to load. Did you scroll down until it loads the next parts etc? Does it stop in a particular place or does it feel more random. When was the last time you optimized the server.