I only have 10 achievements left in MCC, and one of them is to get 500 grenade kill medals in matchmaking. I was at 420/500, played a few matches and got probably ~20 more grenade kill medals, checked my achievement app again and my progress is now at 421/500. A friend of mine also did the Lone Wolf 150k points achievement this morning and didn’t get that to pop either, so it has me thinking that there could be an issue.
Same here, windows 10 version.