In this case a print queue called “lp” intermittently swallows jobs and spits out completely different ones from what was sent.

It is a bad idea to name any printer “lp”. This is the traditional UNIX name for the default printer. CUPS may be set up to do an automatic creation of Implicit Classes. This means, to group all printers with the same name to a pool of devices and load-balance the jobs across them in a round-robin fashion. Chances are high that someone else has a printer named “lp” too. You may receive that person's jobs and send your own to his or her device unwittingly. To have tight control over the printer names, set BrowseShortNames No . It will present any printer as printername@cupshost , which gives you better control over what may happen in a large networked environment.