I had the dream visitor show up one time in the background of the scene where Voss comes to my camp, spotted them just before they vanished after the cutscene ended, but I assumed it was something to do with needing to anchor voice lines to a model? Was there a Dream Visitor line in any of the cutscenes where they showed up?

I've also heard that the game sometimes acts strange in cutscenes where it expects you to have more companions than you do, and will put npcs like Withers, or the Oath-breaker knight into the spots where they should be, but that shouldn't be happening when you actually have companions.