I didn't observed the problem, not fax copy and not from internal printing but the customer had samples, I can't post the samples as it has personal data.

Randomly there are void area on the printed sheets in different areas on the page and in different shapes, it can be a long 4" wide or a short 2" void, they are not straight lines.

The symptoms printing from receiving faxes, or copies (they don't print to this printer).

Any idea?