I started a couple of custom challenges today BEFORE I started playing Firefight to get the 1000 on Courtyard daily. Now on XBL I have 458 Kills (all on Courtyard) but Waypoint Challenge is only saying I have 242. My game history only shows I have played 2 games. I have not quit out of any of the games and killed everything to end each game.
Well, now I have completed the 1000 kill daily challenge and failed my 500 kill challenge. This is an obvious sign that this system is broken. I played 10 games (9 on Courtyard and 1 on Corvette) and the system decided to recognize only 5 of my games. All games played in Score Attack and all games completed with all enemies dead. No quit outs.