Save ended

I’ve been playing Beskar mode recently. On my first save Hawks died and I restarted the story, I’ve been getting back to where I was, still on Beskar mode, when on the Bespin level I simply kill an enemy(none of my players die or are even injured) and it says game over, and I’m sent back to the loading screen with no save. Very frustrating as it has been quite monotonous getting back through the story when I know what happens. Wondering if there is any solution