Annoying stay bug

I was looking through my campaign mission and about to replay a few when I noticed that the mission “the halo” had a silver medal on it. The weird thing is that I have beaten this mission and gotten a gold medal on it and have the acheivment for Palmers pure gold. The stats for each of my mission’s also say that I have no skulls on them which makes no sense because I have all of the skulls.

Any help on this is appreciated this just annoys me, thanks.