This had nothing to do with OCR -- it was due to compression artifacts. Specifically it looked for common patterns and created a lookup table to save space. It's just that some numbers and letters look similar enough to that algorithm that it didn't notice that a 6 and 8 were different "patterns"

And that was the issue -- nobody was using the Xerox to scan the text -- they just wanted it to make identical copies like all other Xerox machines did in the past.