hope you are fine and you have received my message on the phone.
The working parameters are correct so your problem seems related to the material. If possible you can try another roll coming from a different batch.
To be on the safe side you could also check that the measured pressure and temperature during the operation are close to the set values.
Please also note that unfortunately Mr. Luigi De Marzi died in February of 2015 so please forward any request to my side.