Something you might try. Screw a piece of wood across the faceplate and give it a sharp crack with a hammer in the undo direction, I know the shaft will move too but it might just be enough to loosen it. If not, clamp 2 pieces of wood together and drill a hole in them the same diameter as the drive shaft, move them apart and plane the faces where the half hole is. Postion them on the shaft and cramp them together firmly, now rotate until the wood is levered against the bedway. A couple of bolts on opposite sides of the face plate will allow a lever to be placed. Try it, you never know. Once you have got is all sorted I suggest you place a washer made from gasket material permanently on the drive shaft, that should prevent it happening again.
I hope this helps.
