It's not that it's broken, it's just you're using the wrong rank for the achievement.
IIRC, it uses the rank found on your usercard.
I believe the usercard ranking system was used before the whole elo ranking system was introduced. I'm not exactly sure how the ranking for it worked, but yea.
^mine for example
you don't seem to have a rank on your usercard
Last edited by DruggedPanda; Jan 13, 2016 at 05:13 AM.
Reason: added a screenshot that proves my memory was right