Beat Uplift Reserve with a time of 3:25. Well below the 4:00 requirement. Usually a glitched achievement will say ‘Done, unlocking’ and unlock later, but this isn’t the case. It still is locked. When I check my progress on trueachievements.com, there are ‘scores’ associated with the achievement and not a ‘time’. It says I am 86% unlocked with a score of 205,136 out of 240,000.
Scroll down to achievement. Link: http://www.trueachievements.com/Halo-The-Master-Chief-Collection/achievements.htm?gamerid=70442