I don't know if anyone else has ran into this issue, but twice now DEVGRU Dominator Headgear item has not unlocked.
A while back in Core TDM on Collision I earned and immediately called in a Maniac. I proceeded to get the 6 needed kills for the item, but the 6th kill was the game winning kill so I figured the game did not have enough time to register the completion.
Just now however in a Core Domination match on Flooded I earned and called in a Maniac and earned 12 stab kills with it (I seen the "Crab Meat" operation complete before running across the map and killing 2 more) before killing myself at 22-0 from falling 3 feet (?). I never seen the operation pop up as completed during the match. Post match at the lobby screen I did not see the unlock notification in Match Summary with the only operation XP being shown is that from completing Crab Meat again. The item is still locked in my customization.
It has to be 6 different players on the apposite side that you have to kill.
Well that sucks for me. The first time I still should have had it despite the GWK, but the second time explains it, There were only 4 at anytime and I kept killing one poor sap multiple times.