Epson EPL-N1600 Reference Manual page 142

There may be a problem with the Imaging Cartridge. Remove the
cartridge, shake it gently from side to side, and then reinstall it. If
this does not solve the problem, replace the Imaging Cartridge.
See "Replacing the Imaging Cartridge", on page 6-30
Uneven print quality on the page
Your paper may be moist or damp. Do not store your paper in a
humid or damp environment.
Turn off the printer. Take out the Imaging Cartridge, shake it
gently from side to side, and then reinstall it.
If this does not solve the problem, install a new cartridge as
described on page 6-30. Then print several pages to check the print
quality..
Toner smudges
Your paper may be moist or damp. Do not store your paper in a
humid or damp environment.
You may not be using the correct type of paper for your printer.
If the surface of your paper is too rough, printed characters may
appear distorted or broken. Smooth, high-quality copier paper is
recommended for best results. See "Paper Specifications" in
Appendix A for information on choosing paper.
Turn off the printer. Remove the Imaging Cartridge, shake it from
side to side to distribute the toner, and wipe the bottom of it with
a clean, dry cloth.
Clean the paper path inside the printer using a clean, soft, dry
cloth.
Clean internal printer components by printing three pages with
only one character per page.
6-16
Troubleshooting and Maintenance