Oki LP-1040 Maintenance Manual page 247

(6) Poor Image reproduction
The original and the printout differ.
Characters or forms not present in the original are printed.
Some bits are missing.
Vertical bands of 8 mm in width are missing.
An image already printed overlaps printouts made afterward.
Print sample
■Cause and solution
(a) Cause:
Controller malfunction
Solution:
Restart the Printer.
7-18
Possible problem locations
NO IMAGE
- LED head