When I get to the chair in the warehouse, I am able to enter the tunnel and get all the way to the room in the mansion with the automaton, but the mission goal stays at “Sit down and wait in the warehouse before you enter the underground tunnel.”
What do I need to do to advance the mission?
update: by pausing the mission by accepting another mission and then going back to it, I got the initial choice to read, “Enter Marquard’s Mansion” but as I proceeded down the tunnel, without springing any traps, it went back to the message “Sit down and wait in the warehouse before you enter the underground tunnel.”
You are supposed to interact with the chair to trigger a cutscene and get an item that you have to use before being able to leave the warehouse. That you could get out before getting the item is what sounds like the real bug.
Normally after completing the first of the chair’s quests, it automatically starts the second from the tunnel entrance without issue. Seems like it started the chair version, instead of the tunnel entrance version. Curiouser and curiouser.