Act 4 - Benedictus boss bug preventing me from continuing.

I just beat the Benedictus boss in act 4 and the boss hit me with a lightning attack after the boss was already defeated and killed me. The cutscene for the post boss battle played out, and I hit respawn.

Now the quest 'The Search - Enter the Excavated Site' is bugged out. The door to the excavated site is unreachable, and I cannot continue from here.

I have tried dying to respawn, and restarting the game, but the boss keep appearing for a few seconds and disappears leaving me stuck as I cannot progress the quest or even try to redo the boss fight.

This same thing happened to me, killed Bendictus and died to a lightning attack, cutscene played out and can not proceed to the Excavated site. All the NPCs are gone and the door is closed. Reloading at checkpoint and relogging does not fix this

Update: For anyone else who runs into this issue. For a workaround I reset the instance by pressing Ctrl+R on a waypoint and entered a new instance. I went through the map once more and I was able to challenge the boss and proceed on with the quest.

Respawn at checkpoint after the fight, in an attempt to skip the damn roleplay, also produces this state.

Fix by doing what the guy above says.