New Rayvis bug

I've gotten beat by Rayvis probably about 15 times, at least, playing on high difficulty. Now all of a sudden, if I hit him once, the cut scene kicks in and takes me to the second stage of the battle and if I hit him just one more time, he dies and the fight is over. I cut the game off immediately as to not save that garbage. I need to beat him myself. And the same thing happens if he hits me one time—I die from one shot. I've tried rebooting the game already but that didn't fix it. It's happening every time now. One hit kills like we're playing with a Golden Gun. I don't see this problem for anyone else anywhere. I need help fixing this.