In chapter 12, the final chapter, you can't save after entering the core, and that combined with the fact that you can't go and repair your Skells, or get back any consumables in it, combined with the hard bosses, makes ch12 almost unbeatable for a player like me with only one lv50 Skell, without reseting the game to the moment before entering the core. That's why I may NEVER beat this game.