I am playing and am at 33% in and I beat the double Titan part and after that nothing happens and when I watch a walk through video for it after I beat those two the mission completes automatically and then the next objective starts, mine just stays stuck on the objective that I saw finish auto on the walk through video, why is it doing this as I have spent so much time and hard effort to get this far and I don't want to have to start over again, any ideas what's wrong or how to fix it. Thanks so much in advance.