I currently use a Summa DC3 plus printer/cutter. Over the past 25 or so print jobs, I have noticed some yellow smearing/smudges on areas of the printed material. These spots are not always in the same areas nor do they have a constant shape. I have cleaned the printhead, the cleaning pad etc but they still pop up occassionally, mostly near the front part of the print job. Could it be a bad ribbon or media or is there something I need to clean that I haven't yet????