While playing a recording on my Fire TV Stick 4K, when I press the Back button (on the stock remote) to exit the player, the app surprisingly shows the "Preparing your TV..." startup screen for a few seconds, and then drops to the most recent top-level page (e.g., Movies), rather than returning to the recording's detail view like it should. This seems to be a bug.
I'm using the latest v2021.12.17.2308 beta. In the latest v4.0.1 release, the player correctly exits back to the recording's detail page, and IIRC, also exited correctly in the recent v2021.12.13.1653 beta. This issue only happens with recorded content, whereas live content exits back to the Guide or On Now normally and immediately.