I have tried, and it's the same thing, the party cause problem with balls, and PC center crash the game.
I join you my save, if that could help you to debug
1232 - Pierre - 54h 7m - 5 badges.rxdata
I check, and i have a save that seem to be not corrupted, before aya fight.
I remember have save my game right after win against her. And when i load this save, i was teleported out from the arena building, with a error message (not a crash), the cause may be here ?
I join you the save before the fight
Game before aya.rxdata