Weapon Challenge Unlocks Not Unlocking The Weapon

I also have this kind of problem. After the requirements changed for the missions, the SG553R was completed but I did not get the weapon. After joining a match I got the unlock info and left the game early to test it at the gun range. But the weapon is not unlocked and no method listed helped to unlock it. I hoped this would be fixed with the update, but it did not change anything.