I've never had a moment of trouble with my AT PRO.
Today, after detecting for a short while, it started to false when it wasn't being swung. First, it would show mostly "53" and a mid tone. Then, it started to false continuously -- beeps (mostly mid-tones, but a few others) and numbers all over the place.

I re-installed the coil. I put in fresh batteries. I did the 5-second factory re-set.

Moving the coil wire does not seem to have any effect. I don't think the problem is there.
This detector has not seen that many hours of use over the ten years I've owned it (bought new from Kellyco in 2008 or 2009), and it has been pampered -- Cleaned after every use; always stored inside in a protective bag; never used underwater.

My guess is that something went nuts with the processing unit.

Has anyone else ever had this experience. Anything I should try before sending it off to Garrett.

Any suggestions are most welcome.

DavidGC