There might be something to that explanation, but the difference between 40 old coins and 1 due to ground balance on the Nox? I'm not saying it doesn't matter, but that's a dicey conclusion given the possible "user error." You were able to see his technique, so I'm sure you would have helped him with any obvious technique problems. But, you can't put on his brain and ears. Ideally, you'd link two headphones to his machine using the WM08 units and walk with him and listen along. Most of us have likely done the simple, less ideal option and removed the headphones to compare signals. I know I've done this and people have said they wouldn't have reacted to signals I was pointing out.