Chronology of events:
1. Played the game in multiplayer with a friend, a few days after the game is released.
2. We unlocked one new map and require 1 more game to unlock map 3.
3. Days pass and the game receives its first patch.
4. Played the game with a friend.
5. Unlocked map 3 after 1 game and we play this map and the others a few times.
6. The next day, I go to play multiplayer.
7. I observe that map 3 is now locked and requires 1 more game to unlock.
Right now, I am unable to test whether this problem is recurring, because multiplayer matchmaking is effectively broken. There isn't any lobby system or online player count and people, understandably, are not going to activate the player search and simply leave their computer unattended until someone else does the same (with matching filter settings).