I bought a Gillette Rocket in outstanding condition, but there must be some sticky gunk inside the razor, since it doesn't spin as freely as it should. After soaking in hot water/dish soap. the knob spins freely, but tightens again later. Same thing with a Simple Green soak. I bought a good ultrasonic cleaner to try, which works the best so far. Immediately after an ultrasound tankful of dishwashing liquid, it spins great. As the water dries it tightens up a little. I'm waiting to see what happens when I do another ultrasonic treatment with a true ultrasonic solution (Hagerty). Thoughts?