Without seeing it..my guess would be that there is a teeny bit of lint or thread somewhere that you're not finding, so that with every bobbin use, just a little lint can push it over the tipping point. I would take that bobbin assembly out and use a magnifying light, and clean every nook and cranny.

Thanks, I've done that a million times. It's going to another dealer - since I refuse to deal with the one I bought it from. I'm just so frustrated.

MArion