Halo MCC unable to save progress in Legendary run

Currently running the Legendary playlist on Halo MCC Reach (Microsoft Store version if it affects the issue at all). I played the Tip of The Spear and saved at the last part of the mission when I had to save my progress and leave the game. However, when I came back to reload my progress, I had to restart the whole mission from scratch. This won’t be a big deal if it wasn’t a legendary run. Is it really an issue or is it part of a design I am not aware of? ASAIK, the button Save/Quit is suppose to save, unless it is just have a different meaning.

locked at op’s request