Had the Excal out for the 5th time. Towards the end of my last 5 hour hunt, the Excal would would not stop nulling. I tried using my scoop to resent to the constant hum, but as soon as I would lower my coil it would the Excal would go back to a constant null. The scoop reset method has always work well for me. What's the deal???? Any idea what it will not reset to a constant hum? I have hunted in this area with the same settings on 3 different hunts with no issues. Any help would be appreciated.