If I understand your prob, you sweep the coil by a target and get a good high tone and the numbers did not lock on the high because you hit some junk next to the high tone spot. If this is so, the junk target is larger and or shallower than the "good" target.... or they are possibly just too dang close together.
I run into this all the time with my machine. I try several things to get some clear numbers to make my dig/no dig decision. I rarely us the unmask, some do, I just have not found it overly helpful. The first thing I do is sweep the target from different angles. This will usually work because if the junk was on the left side of the good target and I change my seep 90 or 45 degrees in will many times eliminate the junk from being read and my "good" numbers will lock in.
If changing the angle does not work well, then I place the coil over the good sound and wiggle it a bit till I get only the good target numbers.
At this point, if I am not convinced I have the number locked in well and cant get only a good tone, I switch to two tone ferrous. In this mode it take a number of sweeps/wiggles to get the number to lock but I can still tell if it is iron falseing or an actual non ferrous target.
I still dig some targets even if I cannot get the numbers to lock as long as I can get a consistent high tone in co multi tone or a solid non ferrous in two tone fe. The tone and consistency is telling me that there is a non ferrous target there that is more than likely good target. It could be a silver coin, big heavy gold, a brass compact, water hose nozzle, etc.
If am at an old house site I dig all of these type targets. In a school yard, not so much.
Nothing wrong with your machine, we all go through this. You may want to get a small coil also. Something like a 5 inch sunray. I use a smaller coil in some more "trashy" areas to better separate targets. The normal, stock, 11in pro coil that comes with the machine works very well also but slowing down and doing the things I mentioned above.
These things have worked for me. I claim to be no "expert", but I have been swinging my e machine for about 3 years and am pretty comfortable with it.
Oh, I did not go over the basic settings stuff. Get the e-trac book by Andy S. for that stuff. Hope this helps a bit. I know that you will work through these issues if you keep at it. Happy Hunting!
