First question: Is their something im missing? Yes, we all miss something, so the minelab guys can get it.
Second question: What should the ground balance number be around here in missouri? We dont know, just gb it and get er done it takes three seconds.
Third question: How do i rule out emi interference and would emi interference make me lose depth? Well, you are asking two questions in one sentence so I will give you two answers: The atpr does not react to emi unless you are standing under high KV power lines. And....No, emi will not cause you to lose significant depth.
Fourth question: Should i send the unit to garrett and let them take a look? I will answer your question with a question: A look at what?