Game won't advance after Aspect of the Nightmare!

Slight update. There is one of the spiders from the battle ("Darkness") still on the field of battle, but it is at 0/1550 and does not react at all to being hit by any party member, as they sheath as soon as I stop using them. But I have a feeling that it not disappearing is the reason the game won't advance. Nothing I do seems to make it disappear. Also, since this my second time defeating the boss to have this happen, I assume this is not just some random fluke bug because it happened twice in a row.

I do not want to have to fight this boss a third time, or start my entire game again. Please help EA!

Update #2. I went back to a save a little earlier, though still in the same area of the fade. Did a few of those small skill points side quests, then fought the Aspect of the Nightmare again. This time, when that spider (Darkness) showed up, I made sure he was dead before killing the boss and that seems to have worked. The game advanced and the cutscene cued as it should.

Hope this helps for patching or anyone else experiencing this bug, because fighting a boss three times to move forward is not fun.

Thank you for posting your experience and your solution. I was playing through and encountered exactly the same problem twice. Clearing the spider first worked for me!

EDIT:  had same problem, on the 5th try, went thru and focused on killing ONLY the henchmench spawn.  Eventually killed AoN, and the cutscene triggered.

This needs patched.

I just had this happen to me so I hope I can help out someone else, when this happened to me though one of my party(Sera) wouldnt heal, she stood back up but still had the red skull instead of health. I too had left one of the little spiders alive and went to kill the boss instead, so maybe this started it. I had Vivienne in my party so I used Resurgence (even though i used it already I managed to build it back up during the fight) and it healed Sera and the cutscene activated. i was relieved too because I was playing on nightmare. So maybe if you want to be on the safe side use vivienne in case this glitch happens to you