It may have a fault, although it’s more likely that “K Band” is enabled. K Band is used in mobile speed camera technology (camera vans) but the frequency is also shared by a variety of common everyday objects.
Other examples of K Band radar in use include automatic door openers at service stations, and speed warning signs on the side of the road that show your speed on a large digital display. K Band is a very popular frequency used in a number of different products close to roads, so expect a LOT of false alerts.
If you want any chance of catching the speed cameras, you need to have K band enabled. A radar detector with GPS built in means you can eliminate the false alerts you drive past regularly. The radar detector knows where you are, identifies probable false alerts and ignores that specific GPS location in the future.