Blackstar mission bug

Using Lahn the boss battle bugged and no damage was being done to enemies, pots and other buffs stopped working. I died and could not respawn and had to force close client. Re-logged and attempted to forfeit mission to reset with no success. Selected Helms option and went through quests, once I received the weakened eye of desolation I was still unable to place it in the alter or spawn the boss. After forfeiting again and trying to restart it tells me I have already completed the mission. Now I have a Eye of Anguish and a Weakened Eye of Desolation in my inventory and no Blackstar weapon or way to restart the mission.

Any idea how I can get the mission re-started?

 

I haven't done the blackstar weapon quest myself, but helped a friend who had the same bug. There's another quest you have to forfeit and take again with the black spirit. I don't actually remember the quest's name but I think it starts with [Combat]. Hope it helped