I have had my GTI 2500 for about two months now and have gotten pretty familiar with the machine. Up until I got it I was merely coin shooting and now I am ready to go for some of the deeper targets. Problem is that I have dug several 6 to 10" holes showing coins at that depth and come up with nothing or a rusty nail! I seem to be having trouble with anything below 4". Anything at 4" or shallower it nails like a pointing dog! I have tried two diffferent sites which I know has not been detected and should contain some silver coins but so far I have come up empty. I don't know whether I am having trouble pinpointing those deep targets or if it's the machine. I get a ton of signals that say something like E5 at 12" and I know that there ae not that many targets at that depth that size. Any suggestions?