Wrong Return Setting

If the output is double-spaced, but it should be single-spaced, either the tab settings for the printer are incorrect or the printer is adding a line feed after each return. The LP print service adds a return before each line feed, so the combination causes two line feeds.

If the print zigzags down the page, the stty option onlcr that sends a return before every line feed is not set. The stty=onlcr option is set by default, but you might have cleared it while trying to solve other printing problems.