Check the following points to resolve the issue:

1. Check the machine's environment. Conditions such as low humidity and low temperatures may cause this print quality issue.
2. Make sure the media type setting in the printer driver matches the type of paper you are using.
3. Make sure the two gray levers inside the back cover are in the up position.
4. Install a new drum unit.
   > Click here to see how to replace the drum unit.