This a quite a common bug in regular Arma 2 it usually occurs when a player joins a vanilla server and is running the ACE mod .It can also it can happen if you disconnect back to the lobby to switch to different squads and reconnect,it usually goes away after a little time or you go out of the game back to the server lists then reconnect and that will fixes it.Now this really begs the question why are you seeing that in a Dayz server,something aint right