Both of my hp82341A printers suffer from the same problem: The paper advance is not working properly anymore, as you can see from the picture.
When the paper is not advanced as it should be, the printer writes the lines ontop of eachother. I checked the printer before already, everything looks fine. Thus most likely the Rubber Wheels and the Roller Pinchs are worn out, not soft enough. A replacemenet of Roller and Wheels would be ideal, whoever the service manual doesn't tell any diameters or widths.
So first step is to disassable the printer.
Disassmbling the printer was almost no problem, thanks to the service manual. However, removing the flexible PCB from its connector was quite tricky. hp advices you to take a special tool but naturally this tool is not available. I built myself a tool, just a piece of stiff cardboard.