Then use a little of the WD40 around the screws...sqweez a little like described up above around the screw threads/groves.. then screw them back and forth. I would think this would free them up a bit.
Give it a try and let me know what happens. Remember...you dont need to use much. Try to get the threads to the screw down pushers lightly coated with the WD40. Then counter and clock wise several times with the pusher.
This should do the trick.
Mike