This is a minor graphical glitch that I’ve noticed while playing around in my condo. If you up the scaling to make a Workshop NPC bigger in your condo, everything at first appears normal, but if you go near it and look up at the ceiling, it completely vanishes from view before it even leaves your camera range. (The reason I noticed this, in particular, was because one of my condos has a massive dance floor with a lot of NPCs, so seeing one randomly vanish and reappear amidst a sea of NPCs was weird).
Resetting the scaling to its default seems to fix it, I’ve tried this with multiple different NPC models and this bug happens with every one that I adjust the scaling on.