I collected all Ascendant Chests earlier today tuesday before reset). Did not claim the triumph on the triumph page because I had to log off. Just logged back into the game and the triumph completely reset which means I have to collect all the chests again.. in 2 weeks.. ('cause timegating chests makes sense and is fun /s). I suppose this is because of the weakest/strongest/whatever curse week stuff. I'd assume that after the weekly reset the game thinks it's no longer weakest curse week, so it resets the triumph. Before you ask; yes, I am 110% sure that I collected all of them. I also saw the on-screen triumph message once I looted the final chest.