Ive found that since this update and the previous update, all my iOS devices stutter on certain videos.
Nothing has changed except the last two updates.
Ive seen a few people also complaining about this, not sure what has been done but its definitely backend.
If I browse to my Plex server local IP using Safari in iOS (iPad/iPhone), the same video wont stutter any more.
Its something to do with the server and iOS apps.
Apple TV also is having the same issue.