Just noticed the Disappearing Trader yesterday: none of the Trader wagons had anybody visibly on board until I saved and reloaded the game.
And as far as I know, had my first instance of the ‘dis-embodied Wainwright’ a couple of days ago, a torso-less cart driver, but when I checked, it was 1 Wainwright out of 7 on the map, and I couldn’t see any difference in the actions of his cart versus all the others, and after saving and reloading the game the torso re-appeared.
Transient graphic glitch in both cases, as far as I can tell.