Quiet is quite a showstopper, and it isn’t just because she’s got a super skimpy outfit. It turns out she can literally halt your progress in Metal Gear Solid V: The Phantom Pain. If she’s your buddy on one of two missions, you’ll lose that save file.
We don’t exactly know why it happens, but Konami is aware of the issue. Should Quiet accompany Punished Snake in Mission 29 or 42, your save file will be corrupted. The official solution, for the moment, is to not take Quiet along.
Konami is working on a Metal Gear Solid V: The Phantom Pain patch to fix the problem. In the meantime, make sure Quiet stays home when those two tasks come around.
Source: Konami