Hello Storm,
Really, you are describing a common problem. No, not with the SE but the lack of knowing what your machine is trying to tell you, its operator. No, I'm not trying to come off like some sort of know it all. But, I own the SE and have used it a lot in the short time I've owned mine. I'll state boldly and with certainty, there's nothing wrong with your SE; it's you. Here are things I'd suggest doing.
(1)
Immediately, upon turning on your SE "at your chosen hunting site" run "NOISE REDUCTION". If you should change coils, run "NOISE REDUCTION". Never change coils with your machine ON.
(2) Begin hunting, using a slow, deliberate swing. Too fast and you'll likely hear chirping especially at the ends of your swing. Don't scrub, keep your coil raised slightly off the ground. Scrub, if needed once above a good target; a sound good in at least two directions. I like to hear a little noise, the machine's telling me I'm close to the edge of where I need to be. If you continue to hear NOISE and you don't like hearing it, reset SENSITIVITY down 2 notches. I'd recommend avoiding AUTO SENSITIVITY as it's been my experience you'll lose depth.
(3) My settings. I'm set on 32 MAXED OUT more than not and no ground's more sensitive than Colorado's. I normally run GAIN 6-8, I'm in ALL METAL MODE-CONDUCT-OPTIONS:fast-deep with TONE-(Threshold 6-8 VARIABILITY 8 LIMITS 8-10) One thought; if rusty nails HEAR as silver, your SENSITIVITY and possibly GAIN are set too high. You'll need to adjust either-both until the nail HEARS as iron.
(4) Try avoiding too many changes in your settings per outing. You'll confuse yourself if you get TWIST KNOB-PUSH BUTTON happy. Forget trying to figure out all the Discrimination Patterns MINELAB wasted half their manual upon; they are useless IMO.
If none of the above helps solve your problem, you may need to reset your SE to factory specifications. First though, SAVE YOUR CURRENT SETTINGS in USER A. To reset, simple turn your machine off. Wait a few seconds then turn back on holding down the power on button UNTIL YOU HEAR A BEEP. Your display should open in SMARTFIND mode. You'll want to switch to your SAVED USER A mode to continue hunting. Once you get your SE set up for you, there's little left to do but hunt; it's really that simple.
I hope some of my advice makes sense, helping you solve your SE woes and giving you time to enjoy your fantastic little metal seeker!
Good hunting!
GRB