Not sure if an issue or not, but since latest update on TVOS app, when changing channels the last frame from the previously watched channel is visible after selecting a new channel.
Behavior is noticed when watching one channel,. exiting to guide, and then choosing another. The last frame of the previously watched channel is shown for a second or 2 until the new stream commences.
Same behavior with local source (HDHR) and custom (m3u) channels.