During the Freedom's Progress mission, when you are told to place your teammates around the giant blast door, you can trick the game into spawning extra YMIR Mechs. First, position your team accordingly and watch the cutscene. You'll now face a Giant YMIR Mech. Instead of killing it, turn around, and head BACK through the blast door. This will glitch the game back before the cutscene. Place your team around the blast door again, and the cutscene will play. This will spawn an extra YMIR Mech. Repeat as many times as desired, but more than three YMIR Mechs will most likely kill you.