Now that these machines are getting older, I am starting to see this problem more and more. I get intermittent blank copies only while using the ADF. The ADF is not missfeeding or double sheet feeding. You can copy on the glass and the copies are fine. None of the machines that I have had this problem with are connected so I don't know if the problem would show up if printing from the computer. This appears to be an ADF problem so I don't think the problem would show up while printing. I fixed a machine with this problem by replacing the whole ADF. This might be a good opportunity to sell a new machine to the customer, but the technician in me wants to find an answer. By the way, I know about the drum shutter problem.