It seems that when all the prisoners are freed, there is no way to proceed, get to a big door but nothing happens.
The quest asks us to proceed by escorting the prisoners out.
My group and I are experiencing the same problem. We reached the end just before the final boss fight and nothing is happening to progress to the part where we activate the three things (forgot what they were) to open the door. The NPC’s just follow us around and nothing’s happening while it’s telling us to escort them out. Tried waypointing, dying, running in and out of areas… nothing seems to try to trigger the last part.