[bug] "Dark Chambers of Our Mind" quest broken

[Algreth]

After The father assigns teams, I cannot talk to Tharael or Zar'Ah duing the "make preparations" phase of the quest. They both just stare at me and say "busy" when i try to talk to them. I tried reloading an earlier save, but when I started the quest The Father never teleported down after his monologue and so the quest also would not progress. The save file is attached.

[Algreth]

Update: Tharael was being physically blocked by another NPC was was unable to path to Zar'Ah, thus making the quest stuck. I was able to fix it by teleporting out and back again with a fast travel mod. Quest NPCs should't collide with other friendly NPCs for this reason.