Hi everyone!

A client of us who is based out of the country and is a trader bought aluminium sheets from us. After a few weeks, he came back complaining that his clients have returned back the materials as the interleaving paper between the sheets were sticking to the sheets at various spots. The sheets are as such oiled sheets. We haven't ever encountered such an issue. The pictures sent to us, seems as if the sheets were processed (kind of pre-treatment).

Kindly advise the possibilities due to which this phenomenon can occur.