Sound from right channel only

hi all
I hope someone can help as this is driving me to distraction.

I have got a rpi3 with Allo piano 2.1 plus the Katana setup.

I have just updated to v2.779 and suddenly the sound only comes out of the right speaker.

I have the DSP option to Dual Mono so I changed it to Dual Stereo and suddenly the sound is in both speakers. It tells me to restart so I do but when I restart the sound is only in the right speaker again.

I change the DSP back to Dual Mono and the sound again comes out of both speakers I don’t restart this time and all is well until I change the track I’m playing and yet again the sound flicks back to the right speaker only.

I did a complete reinstall using a fresh image it worked for a day then back to right speaker only.