I have worked out how to get it smooth in all browsers.
I have removed the background image and replaced it with an image that is 150% of the width/height and applied overlfow hidden to it's parent.
therefrom I just moved it with GSAP as I would any div and that works perfectly
The working example can be found here:
See the Pen woRKGm by lavandongen (@lavandongen) on CodePen
Though addmitedly this is dodging the problem of the backgroundPosition bug in Chrome and other browser
Marshmallow's post in Bad performance in Chrome was marked as the answer