It is observed that after printing a black-and-white or monochrome document, light and dark horizontal lines appear on the page. Other scenarios observed were;
Reseat the printer's toner cartridge and Imaging unit.
Perform a Power-on-reset (POR).
Print a test page and check if the print quality defect still appears.
Should the issue persist, change the print resolution to 600 dpi before printing document. To change the print resolution, Navigate to:
LEGACY ID: SO8564
Check the paper settings in the print dialog and in the printer to get clean prints. Reinstalling or replacing the imaging unit may also help solve this print quality issue.
Solve your dark printing issues by reducing toner darkness or adjusting paper settings.