Pinnacle of its kind - Primary demon fight does not trigger

Hi!

I'm trying to complete the quest 'Pinnacle of its kind' in the Chamber of the Unforged, quest stage 'Confront the primary demon', objective 'Defeat the undead dragon'. 

When I first opened the doors and triggered the fight with the undead dragon, I realized that I was way below the required level and ran away, effectively 'ending' the fight without defeating the dragon. 

I then left the Necropolis Halls map to do other quests in other areas (among which a few 'main quests' like the destruction of Weisshaupt), and after leveling up a lot I went back to try to resume the quest.

However, when I re-entered the area ('Chamber of the Unforged'). The doors were still open, but the dragon is not there (does not 're-trigger'). The quest marker is still active, but because there's nothing to fight, the quest cannot be completed.

System: PS5, Game version: V.1394416

I hope the information above is sufficient to reproduce the issue. 

(In the meantime, if anyone has ideas on how to progress this quest, I'd love to hear them!)