Description: Print vertical white lines

Possible Reasons:
- Doctor blade deformation or adhesion of toner, impurities, toner cartridge problem
- If vertical white line appreared at the same place after replacing another toner cartridge. It means that the printer laser head has a foreign object, need to remove the object.
Process 1: The problem stopped after replacing the new toner cartridge
Toner cartridge defected.
Process 2: The problem still exsits after replacing the new toner cartridge
Printer problem/batch complaints identification