Bug Description: NPCs wear situational outfits like customs or clothing that's forced on them for situations they are part of. Once these situations are over, Sims are stuck in that outfit. They don't change anymore on their own. They do change if you direct them too.
Symptoms: When changing household to such a family, the member wears an outfit that isn't really assigned to him (not part of outfits) and they won't change on their own.
Not part of this bug: Sims not changing out of Swimwear. If they change into swim wear, they will stay in swimwear until forced to change by another situation or if you change manually. They don't change out of swim suit when leaving the house or travelling to another lot. IIRC this was called design at some point.
Archived thread had around 42 me toos