I am also having a problem with red dots printing vertically down the page. I can run a calibration on the color and it will fix it for a few pages, but it always comes back. These red spots show on colored printing, black and white printing, and grayscale printing. I have changed all the parts (toner, waste cartridges, drum, and rollers) and nothing fixes the problem permanently.
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It is most likely the same magenta imaging unit they are telling you to change in your other thread