Set "Settings > Video player > Playback mode" to option "Stop playback after one video".
Play any video to completion.
Press any non-navigation button (i.e. not Up, Left, Down, or Right).
The device will no longer be responsive to any user input (aside from Alexa, but no commands are able to run). You may eventually be kicked to the home screen, other times it just freezes on last frame. And eventually the device will give user a black screen.
After the video ends you can seemingly navigate per usual and the onscreen clock still updates in real time, but again any non-navigation input will cause the device to become responsive to user input and eventually black screen.
System Information:
Device: Fire TV Stick 4k
Fire OS Version: 6.2.9.8 (NS6298/4760)
SmartTube Version: Beta 19.44
Steps to reproduce:
After the video ends you can seemingly navigate per usual and the onscreen clock still updates in real time, but again any non-navigation input will cause the device to become responsive to user input and eventually black screen.
Obvious temporary solution
Use any other Playback mode
Pertinent Files:
Settings backup: Backup.zip Logcat output: smarttube.log