I sew over my pins too. I always knew not too, but didn't know why until now. I remember running over a pin, it split and machine stopped. Could not find half of the needle when broke. The needle was in bedded in fabric but portion of the pin broke too. A piece of it was down in the bobbin case. I quit for the night. This usually happens if I'm getting to tired and not paying attention. So I watch myself now.