I encountered a different bug here. Before entering the fort, you are asked by Belinda Delaqua to find and bring back a portion of her squad close by. After helping these soldiers out with their fights and reviving their fallen, they went into formation and stopped moving whatsoever. My marker moved back to the fort, but without the soldiers the gates wouldn’t open and I was forced to redo the quests.
Luckily for me it’s right at the start of the quest, so hardly any time and effort were lost.
(Bug reported)
EDIT
I think I’ve figured out what caused the bug. During my first two tries I revived all five of the soldiers with my Spirit of Nature’s skill Nature’s Renewal. This is not supposed to happen, as only one of the soldiers can actually be revived. The other four soldiers cannot be revived in the usual way. During my third attempt I only revived the one soldier and the quest progressed normally.