In my Hardcore world that I made in 1.18, all the villagers suddenly did not load the underlaying parts, or are just showing them in black and white. This did not happen at the beginning, and suddenly that just happened. If the villagers do not have a job they just appear black and white with a circle thing on their head that looks like a farmers hat but is just gray. If they have a job, then the things that make that villager look distinct are there, but the original villager is still weird looking. They still interact with everything normally, and it's not only in chunks that were previously loaded.