HP DesignJet Z5600 - Thin vertical lines across the image; The whole image is blurry or grainy; The paper is not flat

5. Carefully remove any of the jammed paper that you can lift up and out from the top of the printer.
CAUTION: Do not move the paper sideways, as it could damage the printer.
6. Rewind the roll. If the paper is stuck and cannot be rewound further, cut it from the roll.
7. Remove all pieces of paper from the rear of the printer.
ENWW The paper has jammed 129