I had a bug regarding the door but of a different sort;
In my game I only went to the Path of Blood after completing everything in Arx, I had all the pieces and had pretty much finished every quest, but when the Pilgrim ran to the door the door didn't open and couldn't be opened. Luckily, I'd been saving pretty often so I went back to one of those and just ran back to the door and it worked fine that time round.
I think that particular bug came from the fact I think I was saving the game at the same time.
