Backstory -
I've been having performance problems for quite awhile (not sure if was in 15 transition or earlier) with updating tags (renaming tracks, etc.) in that there's a sort of peeving (roughly a second) little hang if I (a) change a track's name, say, then (b) arrow down to put the selection into the next track's name (that part is speedy) and then (c) either try to start typing or press cursor left/right/etc. keys.
Anyway, today I thought maybe it's somehow trying to update tags in files synchronously. So I unchecked "Update tags when file info changes". Didn't change the perf stuff. But did cause amusing situation where I can edit a bunch of tags, see those changes, then sit there for a few minutes, and the see all of my edits revert. For example, had a new CD with tracks named Track01, Track02, etc. Typed in proper names for them. Went to answer the phone. Came back and roughly half of them (not all!) had reverted. Then a moment later the artist I had typed in reverted (such that tracks weren't in the query anymore and disappeared!).
It's possible there's another machine somewhere connected via library server? Some kind of weird "last writer doesn't win" bug?