Quest Resets When Attuning to U'Ghamaro Aetheryte

I have been stuck attempting to overcome a critical bug for weeks now, with no avail. When I go to complete the quest, "In a Titan Spot", I attune to the aetheryte in U'Ghamaro and the game notifies me that I have completed the quest, my duty finder has been update to include "The Havel (Hard Mode)", and that a new trial is now available. However, the quest never completes, as it remains on my duty finder, and none of these event actually happen, even though I am notified that they do.

I also cannot withdraw from this quest to start over again.

I have been referred here from two different GMs and they have absolutely no idea how to fix this "critical" bug. Please help!

I had a full inventory. For some reason, this prevented me from continuing...

Please defer/.