How are you doing? Like leonf mentions, oil all parts just in case, there are joints and oil points in the back as well if I remember correctly. I would tripple check every little tooth in the part that turns the cam, and from your description it sounds like the spiral threaded part needs more oil and wiping off. I use cotton swabs and those velvety microfiber cloths, pieces of soft flanell are good too. Oil the treaded part that turns as you turn the hand crank. Make sure the thread guide (moving finger) moves freely too, it should have a spring action and there are oil points for it. Dried up oil and grime in hard to reach places cause all kinds of hick-ups and it takes a bit of effort to dissolve and flush it out. Spray can oil can speed things up, apply every where a couple of times, turn the mechanism and let it seep in. Eventually turn to triflow or regular sewing machine oil, spay can stuff is usually too thin to lubricate a machine in the long run.