dragon age origins dead trenches glitch

I am playing in Orzammar, I am in Ortan Thaig, when i go to the correct exit to get to the Dead Trenches a cut scene is triggered that is supposed to end with you in the Trenches. It does not work. The audio plays but the video is black or shows a angle from under the floor. The dialogue works, I have to choose what to say. Once it is over, i am still in Ortan Thaig, and usually one of the characters is in a wall or on top of magma. I cannot access the Dead Trenches, once the cutscene plays I get stuck in Ortan Thaig and it never plays the cut scene again. I am playing the fully updated Steam version, Ultimate Edition. I cannot roll back patches. I have tried uninstalling and reinstalling, I used the same save file to go back to where I was. I have considered playing from a much earlier point, but I don't know if that would be worth it to play an entire level over only to have the glitch happen again. I have searched the internet and found no mention of it. The game plays fine at all other times, no graphics or audio problems, it loads normally.