14 medallions of the Order, where are 15? All killed including father

Khaisem demands 15 medallions, while I have all the members of the order, including my father, who gave the medallion of his own free will, were killed. I don't understand what to do!

Help to solve the problem, maybe it's a bug and if so where to go? (I play on xBox series X) that is, the game is original.