A.    The encoder strip is a thin flexible metallic or mylar strip located
      behind the cutter assembly, spanning the entire left to right width of
      the platen on the plotter.
      
      1.    Occasionally, after a paper jam, the encoder strip gets twisted.
            If the encoder strip can be untwisted, so that it is flat all the
            way across from left to right, then the problem will be
            corrected. Try to avoid touching the rear portion of the
            encoder strip, which has the graduated markings.
      
      2.    If the encoder strip gets dusty, or some foreign material gets on
            it (packing, paper, etc), this may cause the error to occur.
            Blowing on it with compressed air may solve the problem.