I would like to add on to this that in my game, every time I load CAS the link option is re-activated. I deactivate it every time because of all the same issues above, I spent hours meticulously designing all 40+ human outfits for this character, but soon as I load CAS and forget to unlink the mermaid, then there goes some of my hard work. It's even changed things like Tattoos and other features, but definitely hair and clothes are all swapped around. The problem for me isn't just that the linking doesn't work as it seems to be intended, but also that it just refuses to stay off. Literally every time I load CAS it's back and now I have to be super conscious of it. Also wearing one-piece swimwear seems to confuse it heavily and it just picks something at random whether I like the look or not if linking is on and then it just changes both sides of the outfit. One time my sim went back to human form with a whole new top and no bottoms on (I do have a nude mod, but this would still just be her standard underwear I mean instead of the swimsuit she WAS wearing) because I had her transform while in a one-piece, and when I went to CAS, sure enough this odd flasher outfit replaced my one-piece swimsuit outfit, hair and all, so I had to rebuild it from scratch. (I have no pics or video to prove this so...just take my word please). Point is, I don't understand how the linking should work...but it clearly isn't like this.
I have the same problem but unlinking them won’t work for me. I transformed my sim two times back to a mermaid and now somehow the scales from the first form are attached to her skin, I can’t get it off. So this means that I can’t even change the scales in mermaid form because then you’ll see two scale ‘outfits’ mixed up on her body. Any idea how I can solve this?