Turn on Background Suppression, There is not a firmware that causes background on copies, and if there was a hardware fault in the scanner it would have to occur on scans and copies, and if there was a hardware issue causing it to print backgrounds in the IOT portion it would have to apply to prints and copies but not scans.
I have a gray background when copying..
On Xerox Altalink C8070.. one with firmware version 101.003.029.03810 and the second : 101.003.038.10200
Do you have a firmware who repair this trouble ??