I looked found nothing rinsed everything off still there cut a new piece same problem different spot felt grainy.
I had a problem with the base paper very slightly shredding from being damp - this after using it a couple of times. It was extremely slight but could be felt when honing the razor. It was like the pea under the princess' stacked pillows. Impossible to see or detect until you moved a blade across the film. Wiping the marble base with my hands didn't detect anything - but the spot moved. It was kinda weird. Rubbing it down with a cloth worked. So... fresh backing paper each time.