The triumph "Happy Haunting Ground" just stopped counting progress and there is no loot dropping from the chest after killing the boss. I’ve tried starting it from the tower and via destinations. I made sure that I stay in the Haunted Lost Sector until the Mission Complete screen appears. My mask is on and kills still drop candy. I still have Spectral Pages in my inventory and they do not get “used up” even though I’m damaging all 15 headless. I’ve already unlocked all pages in Vol 1+2 and the only thing left for me is the triumph. I’ve read that you can finish it on another character but I have only one. Is there any other fix for the bug?