The lower mat on my 210M has a felt upper layer that is bonded to a very dense rubber foam. The foam is helpful since it's compression resistance is a part of the equation (heat and pressure).

I would ask if the thermostat maintained temp. I use Seal Colormount and it requires 190 degrees. Too much temp. will cause as much problem as too little. Cleaning the platen is a pain in the rear. I spent hours with 600 grit sand paper. Release paper is important and also a clean mat board above the print when mounting. The smallest foreign matter will dent the surface of a print.