On the half that doesn't have the PCB, you should see three wiper arms that make contact with the encoder traces on the other half of the encoder assembly. Using the precision slotted screwdriver, gently bend these outward so they protrude further into the air.

Don't over-do it when bending the wiper arms. The amount of bending I'm displaying in the picture is a little on the excessive side. Do not exceed the bending angle I'm showing here.