Please check the following points to solve the problem:

• Make sure that you use paper that meets our specifications.
  Please refer to FAQs, "What kind of paper can I use? " and "What is the recommended paper?".
   
• Choose Thick Paper mode in the printer driver.
  Or use thinner paper than what you are now using.
   
• Check the machine's environment. Conditions such as high humidity can cause hollow print.
  Please refer to Safety and Legal pages in User's Guide.
   
• The drum unit may be damaged. Put in a new drum unit.
  Please refer to the instructions, "REPLACE DRUM".