I have it on my pots too and I think itīs just the nature of howe the
pots are constructed : one "arm" connected to the knob and the arm
moves over "resistance spun wire", and when turned quickly the noice is heard,
like when you drag your finger across a spun guitar string ( e, a, d )
After a few years the noice will get quieter as the pots wear out ......
Cheers !