Car audio issue - no sound from rear speakers

[empezza]

I have an Android headunit in my car, running Android 6.0.1, with Gonemad 2.2.21

All was fine until a week or so ago when I noticed that there was no sound coming from the rear speakers.  Front speakers are fine.   I checked the cabling and all seems OK.

In desperation to fix this I installed POWERAMP, and without any changes to hardware or the front/rear audio setting, Poweramp puts out sound to all speakers.   So it does not seem to be a hardware/wiring issue.

I can't find any setting within Gonemad that would cause this.     Any clues on why this is happening?

[empezza]

Installed GMMP 3 last night and it gives me sound from all speakers! Will give v.3 a run for a while.

[GoneMAD]

gmmp outputs stereo sound.. so thats nothing that gmmp controls. The android operating system routes the audio

[empezza]

Thanks for that.