One person had a problem with the cutscene not being triggered when they teleported to the battle tower immediately after completing the quest.
The Dragon Knight Protection Squad (or whatever)Do you have a save from before completing the 'Down the Hatch' quest, that you could reload and try again? Maybe if you teleport to Broken Valley or Sentinel Island and returned to the fjords, getting the game to reload that area would avoid whatever the problem was the first time.
Try emailing support@larian.com, with a description of the problem and maybe a link to this topic (DKS
support page).
