Black water holding tank

This last camping trip when we were getting ready to leave I was filling my black tank with water to wash it out when we went to dump, well all of a sudden I heard this loud pop, it was the black water tank and the dealer told me it was because the tank was too full, the tank ruptured on top. I have never heard of this happening especially because the tank was too full. Has anyone else had this problem or heard of this kind of a problem?