While pushing down hard on the top plate, move the downshift lever to the right until the top plate snaps into place. As a side effect, this will pick up the loop on the downshift lever return spring. In this photograph, the lever has picked up the return spring, but there is still some distance to go before the top plate will be able to snap into place. Once the top plate is in place, tighten the top plate screw as far as possible. Then use a flat-bladed screwdriver to push the copper-colored downshift lever return spring to the side, while continuing to push down on the top plate (you may have to push in several places). This may allow the top plate to snap down further. If so, tighten the top plate screw again.