HP M1536dnf prints horizontal lines on every page

[LauraOliver]

We have an HP1536 dnf that prints random horizontal lines on each page. Sometimes there will be 3 lines, or 2 lines or maybe just one line. If there are 3 lines they will all be different widths apart. Sometimes the lines are a half inch apart and/or sometimes they are 3" or 4" etc apart. The lines may be ghost lines. They are perfectly straight with varying widths from the size of a fine pencil line to as large as a sharpie marker. They are not always solid and could look like a crayon line,but they are always perfectly straight and horizontal. Any ideas what I can do to fix this? Thanks!