NAD M2 "Protection ,right channel short"

Just took delivery of this used integrated yesterday . Hooked up and listened for two hours .The amp went into protection stating the message right channel short . No wires were crossed or connections were changed . I had noticed the imaging had started to move left previous to the shutdown .I restarted the amp it worked fine for another hour .I then shut it down and went to bed.At the time of shutdown I was playing Peter Gabriels Love To Be Loved .That song is very dynamic in terms of quiet to loud passages and I always find I turn the volume up pretty good . Can loud volume cause a short ? Should I send the amp back to the Brick and mortar store I bought it from .