Yeah, I read that and felt slow for a minute.

Well with my two, my BB broke, but his left knee also won't go down all the way, (the left edge conflicts with the outer leg mold) so I figure it could be QC as well. I have never broken a TF in adult life, and as a kid only "broke" one when my father stepped on one, so I'm always super careful.
My BB works perfectly now, and the snapped part is so hidden you can't see it, and it still works, so nothing was really lost. But it also didn't break all the way through, so that was luck too.
With my CJ, I had no problem other than hood wear at the top corners near the hinges. He transformered super easily, but he was also my second attempt, as I opened BB first.
I now know the comfortable pressure to use, so it may be that I used too much pressure on BB, or it could be that I used the same amount of pressure and the hinge wasn't formed perfectly either, so it snapped under the pressure needed.