Weapon XP bugged

Leveled the RPKM to Level 50. Got no unlock sound, thought well ok, maybe I missed it. After the game endded I went to menu. Gun Level states Level 50, but no Unstoppable Force Skin. See screenshot.

After restarting the game the Weapon is suddenly back to Level 49. So there is some Weapon XP Bug somewhere. Great Cinema. Not only is the leveling totally atrocious with many guns (sidearms anyone?), no, now its also bugged? Can you even program ONE part of the game which does NOT have ANY Bug?