Yep, that or the cog is too thin to get enough purchase between the lockring and cog to stop it from getting unscrewed.
After they've met you...
Love the fact that you've diagnosed and solved a problem even though the OP hadn't explained the symptoms in any way beyond saying he had lockring "trouble" in the past!
Love the fact that you've diagnosed and solved a problem even though the OP hadn't explained the symptoms in any way beyond saying he had lockring "trouble" in the past!