defibrillator problem

My defibrillator was installed in May 07.   From time to time the device will pulse and is visibly quivering through the skin.  It appears to be a spasm, but there is no readings of any corrective behavior when I take a Latitude reading. I have placed the magnet atop the defibrillator  for five seconds and then followed up with a Latitude reading, with no results.  My cardiologist is puzzled, as well as the consultant from Boston Scientific.  

Initially there was suspicion of leakage through the wiring, but has been ruled out following x-ray, impedance check and an absence of any correlation between the rate of the pulsing and my heart rate.  I have recorded my heart rate at 60 bpm, while my wife holds her hand on the defibrillator  and counted 26 bpm.   I also notice two distinct and unrelated rhythms when I take my blood pressure while the pulsing is ongoing. These episodes occur at night, when I am most relaxed, and can last throughout the entire night. In addition, when I arise from bed and walk around briefly, the pulsing ceases.  When I return to bed, it returns shortly thereafter.  Never had a daytime episode, though I can relax enough to nap during the day.  

Have you any clue as to what is occurring?  Has any other defibrillator  recipient had similar complaints?