Hey Grady. I have had the same thing happen to me with just about every machine I have. Sometimes it's like bill said. There could have been a metal object in the ground that is all but gone and when you disturb the dirt, it just plain falls apart and the signal is gone. I think most of these I have encountered were pewter buttons. One other thing it could be is a very small item close to the surface that falls in the hole after you make your dig. This has happened to me quite a few times. The target I am after is right on the edge of the hole I dig and as I pull the plug out, a small amount of dirt and the target fall to the bottom of the hole. If it's real small, I won't get a signal over the hole because the small item is out of the reach of the coil. Next time this happens, get all of the dirt out of the hole and check it. What ever was that gave you the signal in the first place could be in there. One other thing that it could be is a piece of iron like a nail that has what I call a hot halo surrounding it. Well, corroded iron can sometimes produce a halo that will fool the best machines on the market. When a metal object has been in the ground for a long period of time, it starts to break down and emits metallic residue in the soil around it. This can be great if you are dealing with coins because it makes the target look bigger than it really is and your machine will see it much easier. Iron on the other hand can be a real pain in the butt when this happens. Back in the old days, the amount of different metals used to produce iron varied a great deal. Some could have a higher non ferrous makeup and when it starts to break down, these non ferrous metals are mixed into the soil surrounding it creating a hot halo. When you dig your hole, you disturb the soil around the iron and destroy the halo. Your machine now only sees the iron and if you have the machine set up to disc out iron, you will not get a signal. Try pinpointing the entire area around the hole to see if there is some iron that could have fooled the machine. I hope some of this helps and keep us posted on the 1350. HH Tim