Odd shaped documents will not copy without a blank sheet of paper over them - WC 7545

I have some users who occasionally need to copy receipts and other odd-shaped documents.  When they attempt to lay these documents on the copier glass and copy them the machine says "resources required" and will not copy.  It also looks for paper in the bypass tray.  If the users lay a full 8.5x11 piece of paper over the odd-shaped documents they will copy just fine from either Tray 3 or Tray 4 automatically.  Is there a way to allow them to copy these odd-shaped documents more quickly without having to lay a full piece of paper over them?

Thanks!