I'm sorry to revive this thread, but I noticed the same issue (I'm on PC btw, just as general info): although I don't find so many people using the AN-94 there is this bug that doesn't give you any kind of sound feedback when being hit, so basically I have no clue that I'have been targeted by someone; sometimes it could happen to hear just one hit out of four/five but obviously are not enough to understand the whole situation and mostly there is also a misunderstanding that the person who shot me is cheating (but instead is just a sound bug).
I should have also some videos "showing" this bug, but I should check all my records to find the exact moment, extract as clip, merge few of them together and upload here (or on YT and linking here) but tbh I don't know if I have time to do so.