Solved
Weekly Challenge not completing
The weekly challenge, on the list, seems to not be completed and also doesn't count towards unlocking the weekly bonus challenge.
The conditions I fulfilled was the "Kills and assists with LMGs in Multiplayer. Multi-kills count double.".
At the immediate start of the next game I played, the game registered the challenge as complete and added it to the bonus challenge tally.
Still an odd bug, but the solution so far for this one instance seems to be just loading into another game.
