eizner23

You likely sanded off the protection layer on the contacts. They work now but once it oxidizes again it will be tougher to revive. There is something called Caig Deoxit D5 you can use to remove the oxidation from any contacts. It may take 5 rounds to fully wash away the oxidation, i spray, let sit a few minutes, spray again...finally wipe with q-tip, but it works well without compromising the contacts.