Samsung ProXpress M456x Series Service Manual page 239

12) Partial image void
Description : The partial void occurs in the printed page.
Probable Cause
The printer is not installed on flat ground.
The developer circulation in the imaging unit is bad.
The contact between imaging unit and transfer roller is bad.
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Solution
Install the printer on flat ground. Print 10 sample pages for test.
1) Shake the imaging unit 2~3 times from right to left.
Reinstall the imaging unit. Print 10 sample pages for
test.
2) If the problem persists, replace the imaging unit.
Check if the imaging unit and transfer roller are installed
properly.
4. Troubleshooting
4-129