KTS100 MK8 challenge completed but weapon remains locked

Title:
KTS100 MK8 challenge completed but weapon remains locked

Body:
There is a bug with the LMG KTS100 MK8.
I fully completed the challenge "Bullet Storm 1" (3000/3000 damage with LMGs), and the challenge shows as completed.
However, the weapon is still locked in the Loadout screen and cannot be selected.

Steps to reproduce:

Complete Bullet Storm 1 challenge.

Open Loadouts -> Primary Weapons -> LMG category.

Weapon stays locked even though the challenge is completed.

Expected result:
The weapon should unlock immediately after completing the challenge.

Actual result:
Challenge shows as completed, but the weapon is still locked in the loadout screen.

Platform: PC