The toggle switch on that guitar is at the top front of the guitar just like a Les Paul, so I doubt he's brushing the volume knob (could be wrong though). Could it be loose wiring? When it's in the bridge position and it has the volume/output drop does it help if you wiggle/bump the switch (not switching back and forth, but just a little wiggle)? My Schecter does this every once in a blue moon, but if I wiggle/bump the switch it's ok.