I see, are these new saves that you are using, or converted saved from previous versions?
they not the only one who found this issue.
Im playing the game completely new with no saves.
The issue is that when you get the defeat scene from the boss fight you get an error message when you try use the option to load from before the fight.
It gives the error popup message: "Couldn't load the save file: error 31"
I suspect its due to that saves not being created before the fight with the boss.
I checked the saves and the Exit save is completly broken, as the date and time is always set to 1970-01-01 00:00:00
That save is for of course if you wanna start from the very beginning of the game (where it prompt for combat tutorial)
But from what i can see, the saves for the bossfight does not exist.