Every once in a while my HD300 volume drops off to about half the volume it was. It does it on every channel. I saved all my settings, re-set pedal to factory settings, re-booted power, re-calibrated volume pedal, nothing, still does it. Leave pedal alone for a few days and try again and it is fine. Sometimes play a entire gig, 2-3 hours no problems, sometimes play 15 minutes, problems. Any ideas anybody?