子MovieClipのサイズを変更すると意図せぬ親MovieClipのサイズ変更を引き起こし、意味不明

class Main {
	static function main() {
		Logger.trace('movieplayer start')
		Logger.trace('target xml path='+_root.result_xml)

		setupExtendMethods()

		//make the stage stretch and compact depending on the window.
		Stage.scaleMode = "noScale";
		Stage.align="TL"

		_root.attachMovie('Container','container',_root.getNextHighestDepth())
		var container=_root.container
		container.setSize(100,100)
		container.setLocation(0,0)
		container.attachMovie("bordr","child",_root.getNextHighestDepth())
		Stage.addListener({onResize:function() {
			Logger.trace('onResize called')
			Logger.trace('current stage size:'+[Stage.width,Stage.height].join(','))
			Logger.trace('current container size:'+[container._width,container._height].join(','))
			Logger.trace('current child size:'+[container.child._width,container.child._height].join(','))
			Logger.trace('fit container size to stage')
			container._width=Stage.width
			container._height=Stage.height
			Logger.trace('current stage size:'+[Stage.width,Stage.height].join(','))
			Logger.trace('current container size:'+[container._width,container._height].join(','))
			Logger.trace('current child size:'+[container.child._width,container.child._height].join(','))
			Logger.trace('fit child size to container')
			container.child._width=Stage.width
			container.child._height=Stage.height
			Logger.trace('current stage size:'+[Stage.width,Stage.height].join(','))
			Logger.trace('current container size:'+[container._width,container._height].join(','))
			Logger.trace('current child size:'+[container.child._width,container.child._height].join(','))
			Logger.trace('onResize end.')	
		}})
	}
}

 onResize called
 current stage size:679,480
 current container size:694.3,68
 current child size:679,68
 fit container size to stage
 current stage size:679,480
 current container size:679,480
 current child size:679,68
 fit child size to container
 current stage size:679,480
 current container size:679,3388.25 ←なにこれ＞＜
 current child size:679,480
 onResize end.

るるるー、なんなのよこれは。
子要素のサイズ変更したあと親要素のサイズ変更することで解決できるが、オブジェクトが多層になった場合そんなことしてられるか？何かがおかしい。