A few ideas…
I have previously made the mistake of editing the wrong BoxLayout.txt file. Make sure the file you’re editing is the same one SARndbox is reading. Try very large changes (i.e. 20-50 cm) and see if there is any change in the running sandbox. If not, it’s the wrong file.
Try cleaning the Kinect IR lens.
Your Kinect may have failing pixels “on the left side”. Physically reorient the camera so that the bad pixels view outside the box perimeter.