I have had that with Faendal a few times, he went to Tel Mithryn, I still don't know why. to be clear, I had the exact same bug with a non-modded follower.
Racemenu doesn't use Address Library, so it needs to be updated after every game update. And maybe you haven't updated Address Library. At least that is what I can come up with.
They would need to make their own browser for Vortex for that to work. I too would love it if we could rename ourselves instead of wasting admins' time. There is a Vortex extension to allow you to import Steam workshop mods https://www.nexusmods.com/site/mods/114