There are 2 parts subject to wear which affect the disk stroke. They are the lever, and the actuator. The actuator slides on the drop tube and moves the lever, which slides the disk. The lever can also wear, but being steel is less likely to wear than the actuator. I would suggest you replace the actuator.
Also make sure the powder measure is screwed down tight into the Powder Through Expanding die. Adjustment is made by changing the position of the die body in the press frame.
