I cannot unlock my golden sten muzzle

Product: Battlefield V
Platform:PC
Please specify your platform model. PC
AMD or Nvidia Model Number GTX 1060 6GB
Enter RAM memory size in GB 16GB
Which part of the game is the issue happening in? Multiplayer
Which part of the mode? Conquest
Please select your region Asia
On which server did this happen? Every server
When did this happen? (dd.mm.yy hh:mm) Everytime
Summarize your bug I finished the sten professional assignment I, but I cannot unlock the golden muzzle of sten
How often does the bug occur? Every time (100%)
Steps: How can we find the bug ourselves? You can check my unlock list and assignment list and you can find it.
What happens when the bug occurs? I finished the sten professional assignment I, but I cannot unlock the golden muzzle of sten
What should be happening instead? Golden muzzle of sten should be unlocked

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Golden muzzle of sten should be unlocked