Documentation for the Sophos Intercept X Mobile QR code scanner should probably include something about the limitation of the QR code scanner. I created a 61x61 plain text QR Code using an on-line service, and scanned it three times in a row, the three results were:
The actual text doesn't even contain those values, so I installed a GAMMAPLAY QR Scanner from the Google Play store. It scanned properly.
By experimenting, I found the problem to be that your scanner can't handle a QR code that fills more than about half the height of the scan window, and it didn't matter if I was scanning the QR code displayed 15 cm square on a monitor or printed 14½ cm square on paper. If I held the phone far enough away from the print, it read it properly; too close and it gave me random 8-digit numbers. (In case the problem has something to do with the camera, I'm using a new Samsung Galaxy S8.) Here are 3 identical 81x81 test codes at 200PPI, 300PPI and 600PPI. Even the 200 PPI one doesn't scan properly if I hold the camera too close to it, but far enough so the entire code fits in the scan window.
Hi Kent Lion,Thank you for your feedback. We'll add the information into our documentation.