As Craig said, it's normal. See, one of the characteristics of the Excal is that the threshold takes on the tone of the last detected target. If that was a discriminated out target then it can go away completely. And when that happens I will flash mt scoop handle close to the coil just real quick and snatch it away and usually the threshold will come back. No matter, if it doesn't it will as soon as you hit another target.
Also, lose the disc completely. If you run it up any you will lose some of the finer thin ladies gold bands...the ones that usually have the fat-A$$ solitaire diamonds on them.
Thin gold and foil are in the same range. Medium gold and pull tabs and aluminum trash are in the same range. Heavier gold and nickles are in the same range. And if you want to find any chains, they will be very low...back down in that foil range most of the time.
Bottom line is that the best spoils at the beach go to those that dig it all. The Excal gives you an idea how hard you want to work for a target. Like if it's a low growl, you want to work hard. But if it's a higher penny-tone for example, and you're fighting incoming surf and the hole is getting deeper and deeper...I'm probably moving on. But in my opinion, Minelab should redesign the Excal and get rid of that Disc knob. Listen to ALL of it and then dig what experience tells you to. You will get to know bottlecaps pretty much all the time. You will also know quarters, dimes, and pennies. You may get to know those little round plastic juice bottle foil caps too. In time you will know what to dig and what not to dig. But after those first few surprising gold finds that you thought were junk, you'll probably dig it all anyway.