I just recently picked up a used Explorer II after getting my old machine stolen. My last machine had the pro coil on it and worked like a champ but this one came with the stock coil. Now comes the problem, When using this detector with my old settings it is very unstable and it start bouncing all around going nuts. I am not even running it a full power; sensitivity @ 23 and gain @ 8. It acts like there is a lot of EMI in the ground. I have tried at many different locations still the same. When I decrease the sensitivity down to about 11 it quiets down and doesn't bounce around anymore. I tried swapping it out with my stock coil from my old machine, it does the same. I don't know if this is a common thing with the stock coils or this detector is messed up. It also doesn't seem to have the depth that I am use to as well. It detects fine on top of the ground but really loses signal beyond about 6". If anyone has any advice or has seen this problem please let me know. Thanks!