Brother HL-2700CN Service Manual page 328

I-11 Vertically Staggered Image
Phenomenon
Printed image staggered in the vertical direction as shown in print sample (11) of Fig.8-2.
Main Causes
1) Shock or vibration is applied to the printer.
2) Failure of the laser ASSY PU : Vibration from the rotation of scanner motor.
Countermeasures
1) Do not apply shock or vibration to the printer body.
2) Replace the laser ASSY PU with a new laser ASSY PU.
VIII-71