I have had the top thread get caught on something in the bobbin area too. But usually when I am pulling up the bobbin thread before I start to sew. The bobbin thread runs free but the top is hooked on something. I took off the throat plate and cleared out a few short threads. I think they were from "cutting twice" using the foot pedal. (Just a guess, they were short) I also took a clean paint brush and brushed out the lint from the bobbin chase area. For some reason, it doesn't catch anymore. But I do agree with you, it sounds like there is a metal hang up when it happens.