A handful of Xerox devices have been found to randomly substitute characters while performing a copy action, but not an optical character recognition (OCR) analysis. Confirmed by experiment, both the Xerox WorkCentre 7535 and 7556 perform the swap, with a possible eight other devices also by Xerox manifesting the issue. The researcher who found the problem discovered that "patches of the pixel data are randomly replaced in a very subtle and dangerous way: The scanned images look correct at first glance, even though numbers may actually be incorrect."
