I know right xD those games are driving us crazy !
I did what you said, I re-saved the good one over the first two, and when I try to load them... they work. XD
So yeah the first two saves I made were corrupted... for an unknown reason. xD So nothing to do with the slots I chose, I guess.
It works well now, so I hope it will continue that way xD anyway, thanks for all your pieces of advice ! I can do Zenya's route relieved now xD