The shiny substance is likely a sloppy glue job, but shouldn’t impact anything. As far as the not cutting through…how close is it getting?
Make sure you are pinning the material completely flat (we use these Honeycomb Pins) to eliminate any problems from warp, and you might want to run a copy of the Gift of Good Measure on Proofgrade draftboard, then show pictures of the front and the back here if it does not cut through completely. (Support uses it to analyze machine issues.) 