Volume control default glitch?

Hi all, thanks for the great software. I am using it with a raspberry pi and external DAC, and have had some problems with the volume control. When set on hardware, the control works fine for a period. I leave the pi on all the time and after a while the volume stops working and resets itself to 64 (though this does not show on the GUI volume control which displays 0). I then need to restart the MPD to get the volume control working again.

This happens pretty much daily. I have tried disabling the volume control but have the same problem, it seems to default to 64 which is very quiet.

Any help appreciated.