Various | Locked Door Antics on Silent Cartographer
With the door locked, we have little choice but to continue on the mission. (The door was unlocked when we returned after activating the Silent Cartographer)
[Ed. note: see the 'Lock Warp' movie, part of this trick, for a way around this problem. Just make sure that Player 2 leaves the Warthog right up against the door before getting sucked across for the cutscene.]