If any "sex_traits" or "negative_sex_traits" is false in the save file, none of the "unlocked_sex_traits" will be shown in the game list. The person will still get new traits unlocked but they will not be usable until all of the "Unknown" traits on the game list are discovered. So basically in order for a person to get new usable sex traits, you must first learn all of the "Unknown" traits from "Intimate Talk" during a date. If they start with 1 unknown trait and later learn 10 more traits, you can only use the 11 traits after you learn that 1 unknown trait.

in InteractionMainModule.gd   >   func endencounter():  >  instead of using p.person.unlock_sex_trait(i) ,  use p.person.add_sex_trait(i,true)

Or when building the list of traits, change how it iterates though traits and unlocked traits