ik why, i think you put "Separate Shoot: ON", you need to put "shotgun only" or "off"
I had that same thing happen with the noise, i went to P rank a boss but for some reason it didn't have the chef tasks. i think it thought the boss was a level so it didn't show the achievements. it also made me have a panic attack for some reason because i though i deleted a piece of the game's code. But it was because i had separate shoot on.