Having Vanityslots and biome makeover causes a crash caused by biome Makeover on the client side. (Server side, it loads fine, weirdly enough.)
crash-2022-01-22_10.03.29-client.txt

Nevermind, like a dumbass, I forgot to remove an old cosmetic slots mod on my client and for some reason it blames biome makeover for that. Sorry!