[isopede]

Interference is a real problem with FMCW radars, either maliciously in the case of electronic warfare, or accidentally in the case you mentioned, with many radars in the same space using the same frequency band. Wifi and cell phones use time division or frequency division multiplexing techniques, but radars (at least current-gen) generally do not.

There are mitigation techniques like randomization of chirp frequencies, choosing different idle times between frames, and signal processing techniques to try to detect interference and filter it out. In the general case, FMCW techniques will always have interference problems.

This is one reason amongst many others that military radars do not use FMCW but instead coded pulse compression techniques.