A user on a client system runs an application that composes text and/or graphics to create a print job. The application may interact with a printer driver to create output in a printer language such as PCL, PostScript, or HP-GL/2.
The problem is likely in this process if...
The error in one particular print job is not reproducible.
You create a simple test document and print it to a file. Transfer that file to a different client system, and print it to a different printer on a different print server, and there it continues to fail.
What you see on the screen is not the output that you get.
The problem is limited to one particular user or the users in a specific group; one particular client operating system; a particular vendor's printer driver (or a particular version of the printer driver); a particular font or fonts from a particular vendor; certain extended ASCII characters; a particular graphic object, a particular graphic file format (such as EPS, BMP, or TIF); jobs created by a particular application or version of that application; color or shading; incorrect resolution (dots per inch);, or the print job is missing line feeds or form feeds.
A different driver works fine.
If the problem persists when you send a simple textprint job from several clients' systems, the problem is likely caused by another printing process.