Played a co-operative game yesterday. It worked fine as two players and again as three players. However, when the maximum of four players attempted a game, it never progressed.
The game opened and the first wave of attacks happened, but after that when the map should expand etc - that stage never happened. We re-tried the game twice with four players and it would not get past the first stage.
I can't remember the name of the mission but one of the games played was:
Just wanted someone to know.
Nobody can help fix this unless you find out which mission you were playing. Online replay seems to be broken.