The event, IIRC, was over the radio free europe antenna.
It is theorised that the AFCS/ CSAS system was incapable of filtering away heavy and unwanted frequencies from the LRU's that contain it.
The exposure to the aforementioned frequencies caused the aircraft AFCS/ CSAS system to "drop out" and before "mech mode" ( nothing that isn't in Jane's) could be fully utilised by the crew, the aircraft had departed the flight envelope and at such a level as 500 ft was unrecoverable.
TW