Stuck on same quest, but i had different issue.
Meet Azagros. Said i am not ready to accept his cause.
Meet Istiana. Suported her cause. Done her quest.
Returned to Azagros. Supported his cause(i had option).
Lair was generated on map, but when i got to lair, i did alt-f4 inside.
When i loaded quest was unavailable and lair despawned.
I think issue is showing when you try to load when you declined Azargros or Istiana cause.