Solutions
Select the Maintenance > Print Head Alignment > Vertical Alignment menu on the control panel to align the print head.
Solutions
If the print quality does not improve even after aligning the print head disable the bidirectional setting.
During bidirectional (or high speed) printing, the print head prints while moving in both directions, and vertical lines may be misaligned. Disabling this setting may slow down printing speed but improve print quality.
Select Settings > Printer Settings on the control panel and then disable Bidirectional on the control panel.