The Tracker IV amazes me at the performance, and the depth at which it sends a signal. But I'm wondering if it's me, or if I should send the machine back to the factory to be adjusted. When adjusting the sensitivity, and the discrimination, it doesn't seem to make much difference. I picked up a small scrap of aluminum siding only about 1/2" long, with high sensitivity and low discrimination. But after decreasing the sensitivity, and turning up the discrimination level, it didn't seem to make much difference at all. Anyone have the same problem?