im not that informed about the way, the mod dayz is working on, but i found out there is a hack to glitch items and vehicles. Maybe its because of thoose hackers that smthng runs wrong while a hacker uses a hacked helicopter and a real one gets destroyed then he doesnt respawn? just an idea, but if its a one on one rate of destroyed one and respawning it could be that smthng goes wrong if the client (or what ever) is checking for the count of helicopters when one gets destroyed he finds out "oh all is fine, enough helis are spawned" the hacked one disapears and the client wont check again becuase there is no heli which could get destroyed again.... could be, couldnt it?