I don't understand how a worn worm would cause binding, only play. The wear on the worm and roller is minuscule compared to that of the roller and pin. These are slow moving parts. Even without oil, they can go without wear for a very long time. The roller and pin get hammered out from road impacts like potholes. Once the roller has slop, the sector can freely move. In the center, both gears are square to each others. The roller is loaded evenly against the pin. At this point only end play can be exploited. But at either end the roller isn't loaded evenly. It has less tooth engagement and forces are vectored. Now end play has a greater effect and pin slop is now a factor. Hence, greater play off of center. There is zero adjustment to be made on the worm. Just shim the bearings to zero lash. All the adjustment is in the sector screw. The same forces that hammer the roller and pin take out the bearings over time. Anyway, that's my full analysis based on my findings and experience.