Sims 3 sim is sometimes fully nude without being censored...

inkydr3ams  If this only happens when the sim changes into a specific outfit category (everyday, athletic, whatever), try changing only that outfit.  If it happens when he changes into different outfits, you can try changing them one at a time, or all at once.  You'd need to temporarily change everything about the outfits, although you could try reusing parts of the outfits at a later time.