[Flashplayer Bug] SWF slows Down when KEY get pressed and hold

Hello for my actual project i need a event configuration wherein i can hold a keyboard key down and move mouse.
While trying to implement this, i recognized that the flashplayer begins to lag, saving actions in buffer and playback them when the KEY_DOWN event is allready over…

for example i have a

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler, false, 0, true);

and in the handler i got only this:

private function keyDownHandler(event:KeyboardEvent):void {
            if (event.keyCode == 88) manoverDrive = true;

i also do have a

stage.addEventListener(Event.ENTER_FRAME, enterFrameHandler);

in this enterFrame i do animation for a movieclip that is animated regarding the mouse and keyboard action and events…

now when i hold down any kind of key the animation of this moviclip gets slown down if i hold down the key for 10 seconds and then lift the keyboard key the mousemovements i made bevore gets somehow saved and the animation got a playback of the mousmovements…

i removed the keyboard eventlistener and the behaviour stays…

is that an official flash player Bug?