I believe it is "just" a hit reg problem. It seems to happen in waves where one round it feels good, and the next round it feels horrible and unfair. Or just parts of a round. It almost feels like the game is maliciously trying to create a win or loss outcome to psychologically manipulate your play style or reward someone else. But, it's probably not malice, and instead simple error.
Some times 50 to 66% of my bullets don't register. Even when playing in a lobby just against bots. I have one short example on video in the tech support section where EA asked people to provide examples. It's frustrating and beyond control.