I had this happen when I cheated my vamp sim back to human. The withered stomach would not go a way no matter what cheat I used. Here’s what I did and worked for me. I turned him back into a vampire with cheats. It should give you back all the perks and weaknesses. If he doesn’t have a higher mixology skill, like 5 or above, then cheat it so he does. He needs to make the Draught of configuration and drink it first. This resets all perks and weaknesses back to when you first become a vampire. (Make sure you have the ingredients which you can get in Forgotten Hollow or BB) Then The Ultimate Vampire Cure. He will become human and it should take away the weaknesses and perks in his buffs. It did the trick for me. Hope this helps.
