Same problem here on PC. Seems like the problem only appears when you have multiple games saved.
Did some tests with an empty save folder :
- Game A : Works fine can quit and go back without any apparent loss even after creating other games.
- Game B : Can play once, character is considered dead when you exit the game. When game C is created character not anymore considered dead but save won't load anymore.
- Game C : Can play once, character is considered dead when you exit the game.
Tried with survivor and sandbox gamemodes and had more or less the same issue (Character from Game B was never considered alive after creating game C on my sandbox tests)
I guess while waiting for a fix just play with one savegame.