I found the solution to this!
Atleast for my own game
It happens because of MCCC's appearance template system. Mine was set to apply the template when aging up, so when my sim for example gave birth (because that counts as aging up I guess lol) the exact moment the system thought the sim would need to get her appearance changed (bodysliders) according to the template. Go to the computer's MCCC settings -> MC CAS -> Apply Appearance template -> Turn it to manual
Hope this works for others! ❤️
Tried my best to find a solution, and even tried looking through the MCCC settings (they were already set to the manual, as default) . Unfortunately, they didn't help in my case. I'm wondering if it's because the body preset I'm using is from a few years ago? I have a save file I can upload, if that would help.
