Halo 4 - Campaign Problem

So, I completed the campaign on Legendary last night and noticed I never got the achievements. I looked over the Mission Logs and found that the level ‘Shutdown’ was apparently completed on the ‘Highest Difficulty’ but did not show as completed (on any difficulty).

Link to screenshot:

As you can see, it says it was completed on the Highest Difficulty, yet both the Solo and Co-Op icons are blank, indicating it was not completed at all (when in fact, I completed the whole mission on Legendary).

I also have all the rally points for the mission. Earlier I even went to Delta Rally point to make sure I completed it and finished the mission from that point to no avail. It still is marked as uncompleted and I still do not have the achievements or armor unlocks.

Also, my service record contradicts this aswell. It says I have the whole campaign completed on Legendary, even when I’m encountering this problem.
Help?
I really, really, really, do not want to redo this mission from scratch…