Somehow I broke this one, too.
I had two Uta active at once which isn’t supposed to happen if I remember correct. I killed one of them (the sword one) and the other two stayed shielded forever. After 3 minutes I just let them kill me to reset.
Happened to me once. Killed the first Uta too fast. As long as the active Uta needs to cast her shield for the second Uta to go targetable : it bugged the whole fight.
In your case, the two Utas should have gone enraged because the 1st one died too soon.
Probably, it’s easy to break the game with over-dps. Problem is the character I did this on has around 200ip. If it’s that easy to over dps then the script needs tightened up to prevent this.