Fire TV going to standby

So I finally took the plunge and updated my Fire TV to Krypton. It is running Kodi 17.0-BETA6 Git:20161130-654f1b7.

The problem I have is that the Fire TV is going into standby mode after 20-30 minutes even though something is playing in Kodi. I have no screensaver active in Kodi and the Fire TV’s screensaver is set to ‘Never’.

It has now happened with a movie, a TV show and while playing an audio album. This never happened with Jarvis. When I hit a button to re-wake the Fire TV it flickers on and off like it’s making the HDMI connection but then resumes playing. The very odd thing is it is unpredictable. I watched a TV episode last night and the Fire TV went to standby after 20 minutes, but when I replayed that episode it went through a full 50 minutes without going into standby.

Because of the unpredictability I don’t particularly want to have the debug information on screen waiting for the problem to occur (it’s the family machine) so before getting too much into trying to analyse the problem (or more likely reverting to Jarvis), is this a known problem with Fire TV and Krypton or has anyone else experienced similar? I’ve searched the forum and googled but can’t find anything similar.

Thanks