Ok Bap, not the greatest photos in the world, but they tell us what we want.
The centering is FINE!
A blurry shot (unsteady hand in low light) but you can still tell the centering:
Shapeways clearly messed up on the black one.
I discovered there is a very tiny ledge on the stop wall (circled in red).
On the blue one I had to push the screen a little to jump the ledge, much better. I didnt see that ledge earlier when I took the first shots. On the grey one it slid right in and over the ledge. This ledge hides most of the cut glass screen edge. It is very tiny, not sure what the measurement is, but if you doubled that tiny ledge it would make it more forgiving of any irregularities on the glass edge.
BTW, I confirmed I did order correctly. Shapeways must have pulled your Mamu-5mm file by mistake when they printed it.