I hope this helps, the rise and fall mechanism has typically three reasons why it’s stiff. The first is that the worm and rack are just full of saw dust. This can extend down into the bush and cause the handle shaft to be stiff. This is usually a very simple and quick fix. The only complication can occur of the worm has rusted into the shaft marking a little hard to get off.
the second is that the grib is either too tight or again full of saw dust from being too loose. Three bolts and a quick clean and your good to go.
The final problem is the pivot pin for the bracket that holds the spindle. This can be seized, but usually for this to have happened the rise and fall either won’t work or is incredibly difficult to move. If this has occurred the rack can often be missing teeth. Anyway, this is top off and you can access the system. It’s amazing how a drop of penetrating oil can solve the problem / enable it to be removed smeared in white grease and popped back in again for a smooth action.I have onky ince had to drill it out, but this is when the rise and fall would not move at all.
The saw is an absolute bargain!