In the latest release (v3.1.15), rewind and fast forward are not working correctly when using a third-party remote. Channels will continue rewinding/fast forwarding all the way to the end of the buffer with no ability to stop at a particular spot (pressing play/pause won’t stop it either). And once it has reached the end of the buffer, the icon for rewind/fast forward remains on the screen.
While on this topic, rewind/fast forward using a third-party remote has always functioned differently in Channels than other apps on the Apple TV. In other apps, you press the rewind or fast forward button on the remote and it will begin rewinding/fast forwarding. You then press play (or pause) and playback will resume. In Channels, you have to hold down the rewind/fast forward button to begin rewinding/fast forwarding (single press won’t work). Then to resume playback, you release the button. It works OK, but it would be much better if it worked the same as all other apps (e.g. Movies, Netflix, iView).