Smooth operator bugged.

So I just finished Sparton Ops Solo on Legendary two nights ago ( 10/16.) The achievement for doing so (smooth operator) never unlocked. I checked my achievement progress in the in game game achievement tracker, and it only shows I have completed 31 missions and seems to be stuck there. However the game itself shows I beat everything on legendary. 343 or someone can you please assist me with this, as this achievements took a frustratingly long time to get.

Here are pictures / video of the problem.
Picture showing my achievement progress in game: IMG-20181018-010832 — ImgBB
Here is a video showing that I completed all the missions in legendary solo. MCC Spartan ops Legendary solo - YouTube