I have not had one pull thru, but I have also heard several accounts of these pulling thru. My guess is that temperature has a lot to do with it. On a cold day, the knuckle would have cracked, but on a warm or hot day and especially after a bit a of bashing the plastic was softer and allowed for it to give, with out cracking. I bet that once it happens, the plastic will stretch, and allow it to pull thru easier next time.