THE 3-POINT LIFT ON THE BACK OF MY YANMAR 1500 WILL RAISE, BUT IT WON'T LOWER. CAN ANYONE TELL ME WHAT I NEED TO LOOK AT. I HAVE REMOVED THE FRONT AND BACK COVERS FROM THE PISTON AND AM ABLE TO MOVE THE LIFT ARMS UP AND DOWN, BUT ONLY WITH GREAT DIFFICULTY. HELP !!!