Jump two years after the last post in this thread ....
Mine is currently doing the same thing. I'll be using it to sniff around in the dirt and it will start chirping and vibrating wildly. I then remove it from the dirt to look and see what's there, but the Pro-Pointer keeps chirping wildly. I then hold it way above my head (far away from any metal in the area) but it still won't stop! The only way to get it to stop is to recycle power. It does this many times, every time I've used it.
Got it Christmas, so it is still under warranty. Called the Garrett Hobby Division today and they issued me an RMA number, to send it back to them. My only gripe is that I have to pay the shipping fee to get it to them. I know this may be SOP with many manufacturers, but ammunition manufacturers (at least the ones I've dealt with) will send a prepaid mailing label to ship ammunition back to them, if there is an issue with their product.
At any rate, I will be sending it back to Garrett this week for a resolution of this issue. I have no doubt that they will handle things to my satisfaction.