Following a deep rabbit hole from a Tom Scott newsletter led to a series of articles on how some Xerox scanners and copiers using the JBIG2 compression algorithm are randomly substituting one number or letter for another one, typically 6s and 8s.
This is a known problem, both with the JBIG2 algorithm and known at Xerox as a problem with their machines.
wiki wrote:Although the method of PM&S can achieve outstanding compression, substitution errors could be made during the process if the image resolution is low.[10]