One of the biggest causes for the hand wheel not disengaging is gummed up oil between the hand wheel and the main shaft. You should remove the wheel, clean the inside of the shaft bore and the shaft thoroughly then put one drop of oil on it and reinstall the hand wheel. I always mark the stop motion clutch washer and shaft with a sharpie so I can be sure to put it back the way it came off.
That usually fixes the problem.
Miriam had an old 99K she was curious about putting a Chinese repro spoked hand wheel on so she could turn it into a hand crank.
But the hand wheel would not come off. We had to oil with Tri-Flow and let it sit for a while. After that it just slipped off.
So that's my theory and I'm stickin to it.
Joe