Halo CE Legendary completion achievement

Hello Support,
I finally completed all of Halo CE missions on Legendary about 30 minutes ago. Once the final scene was over, I returned to the main menu and my records are showing that I’ve only completed 7 of 10 missions. 1 of the 3 listed as not completed on legendary is saying that I’ve never played the level at all. This is incorrect, as I just got the achievement for viewing all missions in this game in both classic and remastered graphics. Could anyone assist? I honestly don’t have time to re-do these missions over.

Thank you

I love how posts that were after mine have multiple replies and mine is ghost town. I know we all feel the same about doing the Library twice on Legendary. No admin is able to see this is a glitch and that I’ve done every level solo on legendary and give me the achievements? I still have Halo 4, Reach, and an angry girlfriend to get thru.

Suck it up buttercup! Just replay the missions!

Both of us should be reporting that we cannot complete a co-op mission without getting knocked offline.