Campaign challenge bugged?

[FNP_Perro]

I'm almost done with the personal decorator trophy, but actually I'm really confused on a campaign challenge: unrelenting 3. You have to complete 11 missions on realistic (and there are also the other difficulties which stack if you play on the highest). I've already completed the entire campaign on realistic (I have the trophy, I collected all the collectibles and I also have the campaign challenges for completing each specific mission on hardened, veteran or realistic) but it's still stuck on 10/11. I'm currently 2 missions away from getting immortal fame, so I'm hoping there's a mission who didn't count and i'll be able to get it eventually, but it's really strange. Is there anything I'm missing? Is it bugged? Do I have to do something? Has this ever happened to someone? I really ask for help because I put a lot of hours in this game and I tackled almost everything.