Watcher's keep bug

** spoiler about the plot of WK ***

I've fight my way to Demogorgon and ... theres a bug, the game don't seems to recognize the fact I'm using the ritual scroll. theres an animation, if shoots a little ball to everyone around, and that the scoll makes 99999 copies of himself in my inventory.

even if I agree to trick the knights into comming down, and the dude appear, and if I decide to leave orden down there and use helm scroll, it the same, I get 99999 of the scroll, and can't seems to get any reward for clearing it :/