Change the leather out. You might want to try smashing a lead roundball thin and using that also to wrap. I had that happen to two flints out of a batch of 100 flints and it kind of surprised me. Also are you using the 3/4 or the 5/8th width. The ones that broke on me were 3/4 and technically I think the T/C lock is made for the 5/8th.