Metal Gear Solid 5: The Phantom Pain is a huge game with dozens of hours of entertainment. Unfortunately, a new bug is causing some players to lose all their progress.
Konami announced on their website that the bug is triggered by playing two missions while accompanied by Quiet:
There is a possibility that the game stops progress if having Quiet as a buddy while playing "Mission 29" or "Mission 42". This situation can be avoided by not using Quiet as a buddy while playing either "Mission 29" or "Mission 42".
While Konami indicate there that the bug will simply stop the game from saving, they say on Twitter that it "may corrupt your save file" altogether.
Not all players are experiencing this problem. It's better to play it safe, though. Robert Allen Peeler, community manager for Konami, said on Twitter that the save corruption bug can be experienced even if you played through these missions with Quiet previously:
Metal Gear Solid 5: The Phantom Pain picks up a few years after the events of Ground Zeroes. Big Boss wakes from his coma and sets out to get revenge on the group that destroyed his mercenary army. He creates a new army, Diamond Dogs, to help him strike at targets throughout Afghanistan and Angola. As he builds up his army and its base, he gains access to new weapons and equipment. You can read more about the game in our review.
The game's multiplayer, an updated version of Metal Gear Online, will be arriving on October 6th on consoles and early 2016 on PC. Given the bugs in MGS5, Konami's decision to stagger the launch of Metal Gear Online turned out to be a smart idea. Cleaning up the single-player and multiplayer sides of the game at the same time would've been a daunting task, considering the scope of the online features.