I haven't updated my game to the latest patch, from last week (27th/28th February), by the way.
I'm currently playing with twins, and have noticed that one of them only has two quirks. Usually the third would have appeared by now, halfway through infancy (I play on Long lifespan so infancy is 20 days and the infant has 10 days left until aging up). I triggered an example exception with Better Exceptions (since the Active Sim's traits are listed in the exception), and realised that my infant's third quirk is Free-Air Tinkler, so she often pees on her caregiver during diaper changes. Since this "peeing" isn't happening, the quirk hasn't appeared in game. Her sister has all her quirks.
I haven't tried testing this in a game without mods and CC, but I will do so.
So I tested without mods and CC, the issue still seems to be happening. Hopefully I tested properly!
