Is there a name for a word or term that is persistently re-coined?

Solution 1:

I don't think there's currently a word for it, but you could probably get away with calling it a re-neologism. (Although in the case of "sex film actress", the re-phrasing is so pointless even by PC standards that I'd have to label it a "useless euphemism".)

Solution 2:

"sex film actress" is more precise than "porn star" as there are many kinds of porn media (and many kinds of porn) and "sex film" narrows it down a lot. Also, "actress" narrows it down to "female" but that's probably redundant based on the context. So using the phrase "sex film actress" might not be a euphemism nor an attempt at being PC, but rather an attempt at being explicit.

Given that this is not a word but rather a phrase with a pretty obvious meaning, it doesn't strike me as being remarkable. If I described Lon Chaney as a "silent film actor" you should know immediately what that means even if "silent film actor" isn't a set phrase.