Something weird has been happening with my MX5. When I am using it, all of a sudden the threshold tone will go really high, and when I go over a target, the beep tone is a lot higher than normal also, but very weak in volume. I am using 2 tone mode. If I turn it off, and then back on, it goes back to the normal threshold, and target beep. It has happened the last few times that I used it. The last time it did it twice in the same day. This is my second MX5, and the first one never did this. Has anyone else had this happen with their MX5? It is still under warranty until May, 2017.