Also, the RCS of Saman is not that low, remember that mentioned values are for frontal RCS, not for the one from the side, where it will be much bigger due to reflection from its body and especially fins and rudders. 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.