Check the following:

Is the media loaded correctly?

• Make sure that both sides of the Media Compartment Cover are fully closed.
• Install the correct media.

Are dust or adhesive accumulated on the Print Head or Platen Roller?

Clean the Print Head and Platen Roller. For details, see the FAQ: "How to clean the Print Head" or "How to clean the Platen Roller".

Is the print density set correctly?

Adjust the print density and print speed.

Run the printer self-test and check the Print Head test pattern for missing dots. For details, see the FAQ: "How to execute the printer configuration (Self-test) to debug".
 

If the problem still occurs, contact your reseller or Brother Customer Service for assistance.