Both the Archivist in the Unnamed City (who you get the map room recipe from), and the spider that was in the central area between Weaver’s Hollow and Scuttler’s Shortcut, aren’t spawning in single player games. Restarting the game while you’re in the Archivist’s room can sometimes cause him to spawn, but other than that, he’s AWOL. The spider boss just doesn’t seem to spawn at all.
Had same problem with the spider boss you’re talking about. Tried multiple single player saves and none of them spawned the spider. I also play on Xbox One X.