To make this script work properly in MP games, edit dynbr/dynbr_init.sqf and remove the line:
if (! isServer) exitwith {};
What you are seeing is that objects cannot be deleted/hidden when they are not local to the script performing the action. If the script is only run on the server, as it is by default, then only server-local objects will be deleted (players, and player-controlled AI and vehicles, are local to their respective client machines).
I haven't tested this myself, but I'm 98% sure this is the issue based on your description of the fault.