 Other issues are often caused by operator errors, such as users attempting to feed non-compatible cards into the card printer, while other printing defects may result from environmental abnormalities such as dirt or contaminants on the card or in the printer.Reverse transfer printers are less vulnerable to common printing problems than direct-to-card printers, since with these printers the card does not come into direct contact with the printhead.Broadly speaking there are three main types of card printers, differing mainly by the method used to print onto the card.