Mermaid doesn't transform/have hydration need/no band around plumbob

My mermaid is the son between my sim (who's a mermaid) and the townie Paka'a Uha. At first his mermaid form worked as it should, everything was fine. But now at random, it's completely stopped working. He's still registered as a mermaid in CAS, but when playing the game, nothing works as it should. I've tried removing all of my mods and cc, but that didn't change it. He doesn't transform when swimming or in the tub, he still has the mermaid icon on his needs but when opening it he has hygiene instead of hydration, and he doesn't have the mermaid-identifier band around his plumbob. He still has all the interaction options; mermaid's kiss and changing the weather, and he's able to accomplish them. When using these interactions, his legs glitch and behave like a tail, but do not transform.

edit: I've noticed that my two mermaid children with Caleb Vatore are glitched in the same way. Our vampire daughter is fine, however.