You may not consider this a bug at all, but I was very confused by it until I understood what was happening.
If you set playback speed to 1.25x and then start watching a program that is still in the process of recording, it is quite possible your playback will catch up to the live stream. When it does, the playback keeps studdering.
It would be nice if the playback just returned to normal 1.0x speed.
Latest Windows 10 server beta, Latest Firestick beta.