Konami placed an announcement on their latest title Metal Gear Solid V: The Phantom Pain warning players to not bring Quiet along with you as a companion for either Mission 29 or Mission 42. Doing so can possibly trigger the corruption which will kill the player’s save file.
For those of you who have not played Phantom Pain or any of the previous Metal Gear Solid titles, getting to Mission 29 or 47 is a result of a heck of a lot of hours put into the game. If you don’t want to lose your save, you may want to consider taking DD on those missions instead.