"Use these Essences" Challenge completion disappearing.

EDIT : Well, after writing this post, I came back and the challenge is finally "stably" completed. Don't know what happened there but all's good !

EDIT 2 : It is now happening for the other challenges...I guess just like the first time around it'll resolve itself after a little time but it sure will be annoying as hell...

Today I go to complete some challenges, I take my 4 Hatred / Woe / Greed / Contempt essences out of my stash, head out for dried lake and get 4 whites. I use the essences on the, get the little message every time and after the 4th I get the "Challenge completed" popup.
I went from 16 to 17 challenge completed and everything's going fine.
Now I head up for the great white beast for the cruel quests, I open my challenge screen once there and to my surprise... I'm back at 0/4 essences used.

At that point I shrug it off as a visual bug but I still take 4 new essences out of my stash, talk on guild chat to check I've got 16 challenges completed, use the 4 essences, get the challenge, talk on guild chat and I'm at 17 challenges, change zone...and I'm back to 16.
0/4 essence used while still having the items in my inventory !

Now I change char, try out one essence, the progress is there - 1/4 - I log out of the game entirely and come back...0/4.
I create a new char, same thing.

tl,dr : Use these Essences challenge is completed, I change zone and I lose all the progress on it ad well as the challenge level.