Helldivers, which released last week, has a major bug that's poised to ruin games if you're not careful. While the game has a few minor bugs, its most serious one is a bug that wipes your save if your PS4 controller dies.
Keeping in mind that Helldivers isn't a permadeath-oriented game and that none of this is intentional, the nasty bug happens when the following conditions are met: If your PlayStation 4 controller's battery dies while you're playing the game, the game will erase your character progress and spawn a new level one character when you plug the controller back in to recharge. If you don't restart the game before getting to a checkpoint, the new character will wipe and overwrite your save.
Arrowhead, the maker of the game, is well aware of the bug now that it's been brought to their attention via the PlayStation forums and reddit and the upcoming patch 1.03–which is due for release shortly, will fix it. Until then, keep your controller charged or plugged in while playing Helldivers and you should be fine.
Further bug issues and fixes can be found on the Helldivers reddit thread.