The resistor assembly is crimped or pressed together and further disassembly is not possible.

Use a cotton bud and isopropyl alcohol to clean the surface of the resistive element.

Spray a plastic safe contact cleaner in the area of the feeler contacts.

Rotate the dial back and forth several times.

Check the resistance between the purple wire and ground. It should range from 7.5 kΩ to 200 kΩ with no dead spots.