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That may mean that the scanner parts need adjustment. This is not a user-adjustable thing, either.
However... try placing a single original, face-down... and centered and 'even' to the sides of the glass... on the scanner glass. Then copy that once. Does that image come out centered? then you may need to clean the feed rollers in the feeder at the top of the printer, if all the off-center copies are the ones that are fed through the feeder.
But tell me: how much is the off-centered-ness of the defective copies? is it like a rotation of the image a little (as I assumed above) ? or is it more like the copy was made at the wrong end of the glass sheet, a displacement of the image along the sheet without rotation?