A word of warning for those playing Metal Gear Solid V right now as it appears that a save corrupting bug has been found. According to IGN, Konami has confirmed that bringing Quiet along as a buddy on mission 29 or mission 42 runs of risk of your save file being corrupted.
As of right now, no fix has been announced and Konami says that to avoid this, simply don't bring Quiet along on those missions. This bug
Hopefully Konami will release a fix for this ASAP, but at the very least, at least it's not something that completely ruins the game like if your progress was just erased randomly like some other games have had issues with.