Spark Window (AIR NativeWindow) is freezing on move.

Spark Window when using in AIR desktop application is freezing when user trying to move it on screen by the title. In debug application this is just unusable, in release - a little bit faster.

It seems that there is a handler on move somewhere that takes too mach. Scout shows nothing, but if I create NativeWindow manually (not through Spark Window) - everything is ok, smooth and nice. But I cant use such a window, because I can't load flex content there in a simple way.

Code examples:
This code opens spark glitchy window:

            var w:Window = new Window();
            w.title = "Example Window";
            w.open();

And this is smooth:

            var nvo:NativeWindowInitOptions = new NativeWindowInitOptions();
            nvo.systemChrome = NativeWindowSystemChrome.STANDARD;
            nvo.type = NativeWindowType.NORMAL;
            nvo.owner = FlexGlobals.topLevelApplication.stage.nativeWindow;

            var nv:NativeWindow = new NativeWindow(nvo);
            nv.activate();