I spent some time tracking down the intermittent stuttering issues with Plex, and have figured out that the Plex app does not buffer at all. It doesn't load more than about 10-20mb (if that) at a time. And if you pause the movie, it stops loading the movie at all (no buffering), which is just dumb. (Aside: Before tvOS 9.1, Homesharing via the Computers app didn't buffer either. Now, it does. You can watch as it pre-loads the whole movie. And now movies that used to stutter under both apps only stutter under Plex, because it is the only one that doesn't buffer.) I wrote up a detailed analysis on the Plex ATV user forums. It's quoted below. If you're encountering the same issues with Plex, you may want to sign in there, post your problems with the lack of buffering, and request that it try to load the whole movie. From Plex ATV Forum: Bug: Plex App does not buffer, does not load more than a few megabytes of the video at a time.