If the mystery remains it's said---and it really isn't an issue of geometry--then what's it left too, poor construction. Actually it is common for pucks too break, don't know how many I've found through my years, didn't know at any time I would need to keep track of that particular failure. Fact is it's the weakest part of a break chamber--total force pinpointed. And findings/experience depends on just how many break chambers a person in this business replaces in a career. What might seem abnormal to some is normal to others.