Viewport moves incorrectly in a window

I recently noticed a strange behavior for the QML Viewport in Qt3D.

When I am having a Qt3D QML Viewport inside a top level window and move the window, the Viewport is not moving correctly with the window. In y direction it does not move at all and in x, much to fast. I.e. if I m moving my top level window I am moving my scene out of the window. This btw happens only to the 3D elements, not to the 2D ones.

I am also having problems when resizing a window. Most of the times my system completely crashes. But I am not sure if these problems are related.