Weapon Challenge Unlocks Not Unlocking The Weapon

I've had this problem for a few weeks now. As you can see, I completed the "bulletstorm 1" challenge, but the KTS100 MK8 weapon was never unlocked. I've tried everything: reinstalling the game, repairing it, restarting, redoing the challenge requirements, completing other challenges, playing entire matches, etc. My biggest concern and fear is that this same bug might be affecting many other unlockables that I haven't even noticed.