I put a bunch of new notes in with associated audio files. One of the MP3 files had a filename 121 characters long. But most of the characters were Greek, so it was probably about twice that in UTF-8.
Anyway, Anki renamed it “for compatibility reasons” AND correctly updated the reference in the deck.
The minor bug is that the same media check that reported the renaming also said that the new name was not used on any cards. A second media check did not show it unused.