same thing appened to me all the day.
I took the quest and went to kill Lenanzar with a guild mate. We got the chest and I got the quest completed message.
I changed channel and killed him again, and got the chest again. Ended this I went to pick my rewards at Ronua Camp, but as I talked to the quest's NPC there wasn't any quest available on the chat.
I closed the window and talked to the guy again, and my quest got completely restarted.
Since that moment I tried again to kill Lenanzar, without get the quest completed again.
I tried just now to kill Roa too, with a bigger team, but nothing changed at all.
Here's a screenshot with me, the team, the boss chest we dropped and the quest still not completed.
Please fix it as soon as possible since we cannot even get a token compared to other guys with already a craft.