"CMunrock"......Generally, when manufacturers install jacks, they either install them parallel to the frame, where you crank them down from the back, or at a right angle, where you crank them down from the side. When installed at the right angle, they easily rock back and worth when the wheels move. Mounting them parallel is better, but they can still rock side to side.
The best way to mount them is at a 45 degree angle to the frame and rear end. This prevents movement in both directions. Yours may be welded on, but many are just bolted on. Changing the angle so they fit across the corner can add stability.