Those of you out there that use the dual field know that the dual field threshold always sounds a bit like static with a little warbl. My dual field intermittently goes from the normal static warbl to a smooth thresho!d and at the same time loses sensitivity. It still picks up large metal but it won't go deep or pick up anything small. I sent it to Whites for repairs and got it back , however it did not fix it. Anyone have any ideas or have experience with this issue? Thanks in advance.