melee bug! Opp. Teleport/lag skip

There has been 4 plus occasions when ( running and gunning) where if I am shooting another player extremely close and then quickly melee attack instead of the strike hitting the other player, they completely disappear the game does a slight lag. They teleport slightly reappear and are able to gain the advantage... Is totally random so it doesn't appear to be a cheat. But a glitch or bug happened.