[alfazagato]

The wear takes place in the straight ahead position, and typically on full lock you get binding. If you adjust at the straight ahead position it gets very heavy at half and full lock each way. So, what have you done to establish the wear pattern in the screw? Photographs don't give any clue here, and frankly I am not certain how you measure wear on such a coarse thread, but this is where you problem lies I believe.