Cassette lock ring came undone during my ride tonight. I’ll assume it’s lack of maintenance on my part that let it get this far, but I had to tighten lock ring with nose on leatherman pliers and the muck helped it become cross threaded. Still had play in cassette but had to ride home gently with it in this state.

Fully dismantled and cleaned at home, some indents on freehub spines that gave slight resistance to fitting / removing cassette. Steel sections on spines are fine.

American classic hub BTW.

So, keep riding? Or replace before something worse happens?

Just file em down and refit the cassette. I’ve done that when I put a cassette without an aluminium carrier on a hope alloy freehub, well maybe 3 cassettes now, still running fine. Having said that I’ve got no experience with an American Classic hub.