So after i encountered at least three Quests bugged for me i searched a bit in Guild and tried to find the point of bugged quest like the Balreth one.
Nearly every bugged quest i encountered had the same problem.
One or two points i had to do werent interactable sometimes they were marked as a goal via arrow sometimes not. I worked arround that with an amount of relogs. It seems that the bug has to do with the phasing system. Some phases are buggy and create non interactable objects. I tested that out with guys in different phases and relogging or traveling to them.
Perhaps that helps a bit to route the bug out.
Involved Quests:
Balreths Death
The Brothers will Rise again
The Ritual of Anguish