Please check the following points:

• Make sure that you use paper that meets our specifications. Click here to learn what kind of paper you can use.
• Choose Thick paper mode in the printer driver, or use thinner paper than what you are now using.
• Check the printer's environment. Conditions such as high humidity can cause hollow print.
• The drum unit may be damaged. Put in a new drum unit. Click here to learn how to replace the drum unit.