Whipped it off to take a look.
Looks the blade on the rotor arm has actually cut into the 8 contacts.=20 There appears to be a worn rough edge, rather the normal smooth square=20 cutouts.
The very tip of the carbon button is polished but the carbon is still=20 intact.
Might be worth trying a cap and rotor arm as they are so cheap anyway.
--=20 Carl Robson Audio stream: