Mine generally don't. The rings will get trashed if they slip, but I've barked the bejesus out of carbide balls, went back to the pits and re-sanded my rings, and the whole diff was butter smooth once again. You can definitely flat spot anything, and NON-carbide bare steel balls (like $2 losi balls) are definitely one slip and flat, but I rarely flat spot carbide balls unless something really bad happens like the bolt backs off due to a bad t-nut.