I tried cycling through the frequencies - 5khz is immediately noisy -- all other frequencies are clear at first then get the constant chatter. I took off the coil cover as a last resort and found a quite bit of black sand and dirt from this morning. I think that may have played a role? Machine seems to be working better, but still getting chatter in the same areas that were dead silent during testing all afternoon yesterday. Lowering the sensitivity seems to help, just seems odd that I was running factory settings at 20 sensitivity all day yesterday in the same yard without issue, but now need to dial the sensitivity in half for it to work silently.