You may have a tiny little piece of dried up oil somewhere in the reverse area or in the feed dog area. It can be hard to track down. I don't know if your repair person can do any better on it than you can. Give it some more time with the oil. Drop a little oil on it - then turn the machine on it's side then turn the machine after a while. Keep turning the machine. It needs some time out. I wish somebody hadn't run off Mizkaki by calling her a know it all in a pm. She really would know how to fix this one. You might try sending a pm to her and see if she would answer.