Is that bobbin case coated in dried oil? Does that come off with a little bit of rubbing alcohol on a Q tip or is that just the lighting? I would be cleaning that up and clean up the little spring, too before I did anything more. If rubbing alcohol doesn't work maybe naptha. Some times the dried up oil doesn't come off that easily. It also looks like the tension might be tight but if you pull that spring off it and clean it inside and out, then put it back on according to Tammi's instructions you should end up with a good bobbin case.