Yep, it was the first door! Your approach sounds interesting, but maybe some hint to the player that they will die if they respond? Even after dying I had no idea that was the cause! Is there some in-game reason that could be worked out, as to why answering a radio immediately kills you? You could then give a hint at that after death. Just thinking of how you can make sure players don't give up at that point. :-) It's a really ominous-seeming scenario, so it would be good to make sure they experience the full thing. Good luck!