It sounds like the conductive carbon has lifted, and is causing grit on the wipers to sound like sand being crunched under it.

The carbon comes away very easy when i scrape some away to make no load pots, but it shouldnt come away like that on a new pot.

Heres a 500k pot i have taken off some of the carbon to make a no load (where the 2 lines are), that ring is where your problem will lay.

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