All behemoths, demons and night stalkers are fine. That issue DID exist on 18.4/DF V2.51 (in the experimental branch) but I updated that on... monday I think? I don't remember. Last few days have been a blur. But I managed to fix it on that branch.
Running 18.4(b3) (Sorry should have mentioned that in my first post)
But redownloaded the mod and installed and it fixed the problem. Thanks so much for an amazing mod and the support