It is typical of worm and roller and also recirculating ball steering boxes that they have to have the play set right on center because they are designed with extra play off center in order to avoid binding (which can cause cracked castings) if the play is adjusted later to compensate for wear. It is important to be sure that the actual box is on center (not necessarily the steering wheel position) before attempting to reset the play -- on most such cars you do this by cranking the box from one extreme to the other with the linkage disconnected and finding the exact midpoint in its range, but if you carelessly take up the play in anything but the center position, you may find the steering binding as it passes true center.