I bought my first T-2 in the spring of 2007. And I traded for a second one since. Normally I run it with full discrimination most all the time. This year I have noticed that I am digging lots of pull tabs, beaver tails and bottle caps, that I never use to. I don't pay alot of attention to the screen, I just sort of hunt by ear. I figure it is an internal problem, but was wondering if a bad coil could cause this? I also notice that I am getting much better depth with the back-up machine. Both are 6.0 machines. What would cause I detector to get out of whack? Time? Heat? or being bounced around in the truck of the car? I figure I will be sending it in, but is there something I can do to prevent this. Thanks for your responses.