Defenders can open the doors on castle 3, but appear and act differently for people; this also happens with the gate. So the door can look and act open for one while its closed for someone else. I also got elasticly stuck in the middle right door (the door towards the gateroom from the room that the siege tower ends at), so I could move past the door but would warp me back after a second.
Also you can fall onto the gate from the gateroom and get stuck, or just get stuck at the top of that hole.
He is stuck there.
The gate also misaligns and gets stuck open.
These stairs extend to far down.
Bodies float off the siege tower as it moves.