I've used an Escort 8500 for several years and from time to time it would go into a self-calibration mode, but only in the parking lot of a diner I frequent for breakfast. Sometimes it would flash and tell me the unit needed service, but if I restarted it, it worked fine - once I was far enough away from the restaurant. Then, about a week ago, I was driving along the Merritt Parkway and in did the same thing. On my return trip - within about a mile of the first time it happened, it did it again!!! I finally called Escort and they told me (which was my guess) that if a cell tower is too close, it can trigger that kind of issue...
hm-m-m-m...

 

I've got the same one, and that happened to me a while back. I replaced mine, and the new one never gave me that problem. I've hade the newer one for at least 2 years now.

 

I've been using this one for about five years now - probably due for an update...