There's currently a bug with the acquiral/removal of sex traits. Sometimes after learning them, it doesn't appear, and sometimes it doesn't remove the negative traits. What I noticed is that the traits are added/removed to the wrong character, i.e the wrong character in the end message has "Character A lost this trait" but actually character A never had this trait, character B had, but didn't lose it. It's the same with adding traits, the text message says they learn it, but then nothing shows up. This issue seem to matter only in group sex actions.
EDIT: Apparently this could be a misinterpretation of undiscovered sex traits, and working as intended. See https://itch.io/t/2360962/bug-in-sex-traits