Kanu and The First Herald disappearing.

I killed Kanu and The First Herald but died at the same time, the quest wasnt completed and I wasnt able to go through the door behind him. When I attempted to restart the fight Kanu has flown away immidiately. Restarting the game/steam/computer didnt help and respawning at chekpoint didnt help either. I am not able to progress the game because of it.