Unfortunately, printers are tangible. Users can fiddle with them, load paper, change settings -- which automatically makes them experts on how they work, right?
A printer at a warehouse randomly goes out of whack, printing lines on top of each other and skipping other lines until the document isn't legible. The IT pro and the foreman hatch a plan to catch the problem in action, which includes the IT pro racing 100 yards and up two flights of stairs to no avail.
Then they notice a worker go up to the printer and repeatedly press a button, and a few seconds later the printer goes crazy again. When confronted, the worker explains how "Pushing that button makes it print faster." Not even close, buddy.