Hi Leo,
You have an industrial machine. You have to have the pedal pressed a little to get the handwheel to move manually. Don't know if that has anything to do with anything.... but it might.
I have a couple thoughts. First, you may want to adjust the presser foot tension so it isn't so tight. It's the screw/knob on the top/left of your machine. Righty-tighty, Lefty-loosey.
Second, the linkage may just need a good cleaning and oiling. If you follow what moves as you press the knee lever, just make sure everything that's supposed to move, does. Tri-flow Superior Lubricant works better than regular sewing machine oil for gummed-up mechanisms.
I'm not sure what you mean by the "running wheel at the bottom of the pressure pin." Could you post a picture?