I was considering a polishing kit but have never used one before. Good results for you with no metal loss, however? Might be something to consider. The star seems to grip the case rims well, so I doubt that's the issue, but of course I could be wrong there.

On the bright side, since it isn't a 95%+ collector piece, if worst case scenario I have to move on to a replacement cylinder it won't be the end of the world.

Many thanks, and a happy new year!