George, it sounds like you are getting some falses off the edge of trash or disc. out targets. This is partly due to running a high sens. and sweeping too fast. The Explorer is probably showing the last good reading it got off the false then when you sweep again (probably slower) it doesn't produce a target sound because it is in the disc. out area but the 28 stays there from the false signal as the last ID not disc. out. Sound will always be ahead of the digital or cross hair screen and good target sound must be present first. I don't even check the screen unless I am getting a good tone.
If you are getting intermittant good tones in one spot, go to pinpoint and determine the exact location of the target (or targets) then sweep the coil an inch or two in each direction over the target in disc. mode. If you don't get a good signal doing that, it is probably a false you picked up off the edge of the object which is probably trash. Also, try sweeping the target from different sides if you suspect a good target with or next to the trash and see if you can get a good repeatable signal from one side. Try running with a slight threshold tone and it should fade over the trash objects also alerting you to the trash.
And, when you pinpoint, try to determine the size of the object. If the pinpoint sound stays on as you sweep over several inches you can bet the object is not coin size. Do this from several directions to identify long narrow objects or wires.
