Here's a simple code to demonstrate the problem:
player allowDamage false;
player addEventHandler ["HandleDamage", {
systemChat "EH 1";
_this#0 removeEventHandler ["HandleDamage", _thisEventHandler];
}];
player addEventHandler ["HandleDamage", {systemChat "EH 2"}];
player setVelocity [0,0,-100];The above code will only show "EH 1". If the removeEventHandler line is commented out, both systemChats will be shown.
This bug is similar to doing:
_array = [1,2,3,4,5,6];
_newArray = [];
{
_newArray pushBack _x;
_array deleteAt _forEachIndex;
} forEach _array;which will give [1,3,5]