I would go to a different repair place. a similar thing happened to my friend with her viking embroidery machine. everytime she took it in locally the woman would tweek it and charge her 100 bucks and it would work for a month or 2 . Finally she asked me where else to go and we found another repairman further away but worth it. He replaced her whole bobbin assembly which was worn from so much sewing and did 3 updates she was missing. It has been going like a charm now .