Halo CEA (X360) No Coop Saves

Alright so I got Halo CEA Xbox 360 Version back in March and played through Pillar of Autumn and Halo on Legendary Solo until I got to The Truth and Reconciliation where I gave up, then yesterday I got a Coop partner and we did together all missions from The Truth and Reconciliation to Two Betrayals on Legendary and then decided to take the 3 last missions some other time. Now 5 min. ago I decided I wanted to jump in to get some of the skulls and terminals we skipped along the way and I see I’m back at Truth and Reconciliaton with no completion and the skulls and terminals we DID pick up are now gone, the other guy commented when we were done that on his screen it said we did Assault of the Control Room on Easy even tho we did it on Legendary and I took a screenshot of my screen were it was correct to show him that his game was just bugging out. So I have a screenshot as proof that we did come all the way to Two Betrayals and now the game has pushed me back and even on my Service Records page for Halo CEA (X360) it says 0/10 on both Solo and Coop, what the -Yoink- is this -Yoink-?

Picture proof: https://www.trueachievements.com/gamescreenshot.aspx?gsid=21262613