As far as my own experience goes, there can be an error or two slipping in when loading an area. Most of the time it is solved by quitting the map, waiting and going back in as it reloads correctly (hopefully).
To give a recent example, there is the rat buyer in Vallaki (still a pretty prominant NPC) who, when I loaded the map he was in, had shoulder pads with a "mirror" texture, which reflected the colors in room compared to the usual texture of them which is tanned grey.
Sometimes I also see NPCs without bodies due to the armor model not loading properly, so I wouldn't be too worried and just call it luck?