Please check the following points:

• Make sure that you use paper that meets our specifications. A rough surfaced paper or thick print media can cause problems.
  To see what kind of paper you can use, click here.
  
  
• Make sure that you choose the correct media type in the printer driver.
  To see what kind of media type you can use, click here.
  
  
• The problem may disappear by itself. Print multiple pages to clear this problem, especially if the printer has not been used for a long time.
  
  
• The drum unit may be damaged. Put in a new drum unit.
  To see how to replace the drum unit, click here.