I agree with WJL, excessive pressure was the culprit. The question is "what caused the excess pressure"? Excess headspace does not do that. It could be a double load in one cartridge( or excess load less than double), which may not have occurred in the other cartridges. I believe you will never know, for sure, what caused it. If it were mine, I would just either shoot Rem. or my handloads using Rem. brass.
Mike