Qt QML application fails to refresh window after resize in both horiz and vert directions.

Built several QML apps using Quick2, and they all demonstrate this issue.  For example, using QQmlApplicationEngine with a qml ApplicationWindow and just a few layouts and controls.  Run app and it shows correctly.  If I resize width only, it paints correctly.  If I resize height it paints correctly.  But if I grab a corner with the mouse and pull, it leaves a "shadow" image of the old smaller window and does not repaint correctly.  This repaint fail happens with several of the Qt examples also (gallery, etc).  It only fails if the width and height are adjusted at the same time.  If a field has focus when the window is resized, like a TextField, then the repaint works.