Photocopying has always ranked among the more tedious of office chores – and now it seems that some of the machines may have been working against us all along.

A German computer scientist and blogger has identified a glitch in a range of Xerox photocopying and scanning machines which causes them to randomly alter numbers in documents. In a statement issued today, the US firm, which holds a Royal warrant and is over 100 years old, said it took the issue “very seriously”, adding that the problem lay with the factory default settings.

In one example, David Kriesel who is based in Bonn, found copies he had made of construction plans had altered dimensions of some of the rooms. One Xerox printer had enlarged the square meter of a room from 14.13 m² to 17.42m², while another shrunk it from 21.11 m² to 14.13 m². Mr Kriesel found the copier would often change the number 6 into the number 8, and vice versa. He said the issue arose through an “image compression” fault, linked to how the scanners shrink the file size of scans.

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Mr Kriesel identified two models affected – the Xerox WorkCentre 7535 and the 7556. However, since then he said other users had reported problems in other machines. On his website, Mr Kriesel complained that Xerox had been slow to issue an explanation for the error: “I learned in the last days that a lot of people worldwide seem to have run into the same trap. I got around 200,000 hits and several mails from people experiencing the same errors without a clue where they come from. A notice to the public would have been nice.”

Xerox said: “The problem stems from a combination of compression level and resolution setting. We do not normally see a character substitution issue... However, the defect may be seen at lower quality and resolution settings.”