I have seen that deformation before. if you remove or modify the deformer that comes within the body, like for a no smol shoulders mod for instance. the feet break. and the maker of that mod had to included a prim you had to wear or fuse to the body to fix that.
aside shifting from a feral or miniature avi there should be little else that can cause this. kemono does not respond well to other body deformers that are still in effect before its put on lol.