Amp Volume Increasing On Its Own

Recently, a couple of times when I changed radio stations on my Squeezebox Touch, the volume on my integrated amplifier (Myryad MI240) began increasing on its own for no apparent reason. As it grew louder, I reached for the volume knob on the amp. It would turn but had no effect in either direction. Scary! At least the volume buttons worked on the remote control. Whew! Other times, everything works normally. Stumped. Suggestions?