I've just found a speculation (allegedly from Russian war bloggers) that Ukrainian Tu-141 drones use transponders and while mixing into Russian traffic they squawk 7600 or mimic some other flight nearby thus wreaking havoc into traffic control. I am not sure how plausible this is but if true this would explain why was the space around Saratov closed for a while and it wouldn't be the first time when Ukrainians used some unorthodox measures to cause wanted effect. Stuff for another future Hollywood film.