I bet it's thread or something binding the bobbin spool. All my machines are easy to remove screws and take the housing off so I can see immediately what is wrong. I have saved many $ by finding the problem myself. My computerized machine I took it to the repairman and said I wanted a service charge for him to show me how to take the housing off and put back on, what not to touch and what is okay to touch. I told him I was moving away so he wouldn't be servicing my machines anyway so why not make some money showing me how. Worth every penny.