Can't unlock SMG 08/18 Optical despite completing the requirements

Can't unlock SMG 08/18 Optical despite completing the requirements

While I was attempting to obtain the SMG 08/18 Optical utilising my strategy involving anti-tank mines, I noticed a delay in which where the requirements page didn't update for a second, but then updated a second later. While I was continuing to utilise my strategy, I noticed a discrepancy involving my 'anti-tank' kills, as the game stopped recording my tank kills with the anti-tank mine, despite those kills being legitimate, and done with methods that worked for the first 2 anti-tank mine kills that counted. I tried again and again, and I could vividly recall at least 3 tanks destroyed with the anti-tank mines, meaning that I should have gotten the SMG 08/18 Optical, but the counter never rose up, and is stuck at '2/5'. For those who's curious, I did do the automatico challenge, where you're supposed to kill at least 50 people with the automatico, meaning that this is the only challenge I have to complete in order to obtain the weapon. From this complaint, all I suggest the staffs reading this post do to my progression is to unlock the SMG 08/18 optical or not after thorough analysis of my past conquest games, where I definitely remember destroying at least 3 tanks with the anti-tank mine. Thank you for reading my post.