If Tri-Flow doesn't take care of the problem, you might have to move to a heavier cleaner, such as PB Blaster or kerosene. But I have a aerosol spray Tri-Flow oil and I LOVE it. I can spray it on most any sewing machine problem, go away for a day or two, and when I come back to work on it, it is free or at least much better. I think I bought it directly from the manufacturer. For normal use, though, don't overuse. One drop per where metal meets metal is all you need.
Joe, I appreciate your expertise. You and I have similar interests in vintage machines and similar skills. I am a certified sewing machine mechanic; in fact, I'm teaching a class in that subject tomorrow. I would not be surprised to find that you have a similar background. Do tell!