Even when starting a complete new Showcase Mission and you die, you'll be unable to load the autosave.
It will just give you an error message that says something like "You're unable to load/edit this mission because it is dependent on content that has been deleted [...]" followed by some items that the game thinks are not there anymore or something (see screenshot).
Usually these kinds of errors appear when you try to load a mission, that you played with a now deactivated addon, but as i said, it appears also if you start a completely new Showcase Mission.
I'm really angry with you Bohemia, people spent so much time reporting and coping with bugs, that they should spent PLAYING this game. I didn't pay for this game to be your beta tester. I hope you know that no other studio would get away with this, but i tell you this one thing, if ARMA 4 is anything like this, i'll keep my money and my time far, far away from you. {F24105} {F24106}