This has happened once or twice to me before. Did you hear the crunch of the wrapper as it was splitting? To me, that's once of the worse sounds I could ever hear while smoking. Snap, crackle and pop.
I'm not sure if poor construction, poor handling, high humidity or combination thereof are to blame, but I would double check the conditions in your humi. If they look good, I second dry boxing for a day or so before smoking.