That sounds like the needle was not in quite right. You can effectively advance or retard the timing by turning your needle every so slightly. when you move one way vs the other, this can get accentuated and then cause problems like shredding or breaking. The good part, most LA's are really easy to adjust timing on. I knocked mine way out of time once and DH had no trouble resetting it. It's sort of like the weakest link. But I'd rather have the needle bar slip than something break or bend.