My bet is that a failure to detonate was due to the faulty radiofuse - remember that the newest of these missiles were manufactured around 1990, and by the time of these trials have already exceeded their guaranteed shelf life.
Fully agree with your assumption.
Hpasp Free SAM Simulator, "Realistic to the Switch" (U-2 over Sverdlovsk, B-52's over Hanoi, F-4 Phantoms over the Sinai, F-16's and the F-117A Stealth bomber over the Balkans.) http://sites.google.com/site/samsimulator1972/home
