Ever since the last update saved progress doesn’t load? Please fix this is unplayable it has been like this for nearly a week. You can go back a save point but then you die and bang quits back to the start screen. :-/
Have you applied the hotfix from today? If you haven’t had an update to Halo 5 today, restart your Xbox and boot the game again. The hotfix is for fixing campaing crashes with saved games 