You likely have to take out the bobbin case and clean, I always get 201s jammed with dust and lint down there. It's always much smoother and quieter when it's cleaned. I would spend some time getting oil into the holes, joints, cam actions, etc under the base. Check if the oil point in the screw in center under the bobbin isn't clogged, poke a pin or tooth pick down there. If it's clean just oil the race, there is a sort of cut in the hook and race that turns under the bobbin case. I would give all the oil points both a second and third round of oiling.