When I was saying I had fixed the problem of the aspect ration not updating, I meant the aspect ratio of the 3D Preview and not the render node param of the same name. If you change anything which effects the aspect ratio of the 3D Preview, which would be the image width, image height, aspect ratio or pixel aspect ratio params, the 3D Preview now updates to show the correct aspect ratio immediately. I hope that clears it up.
Regards,
Jo