Canon imageCLASS MF275dw Wireless All-In-One Monochrome Laser Printer - Manual (Page 525)

Smudge Marks Appear on the Back Side of Printouts
94LS-0EW
Troubleshoot by checking in the following order:
Are You Using Paper That Is Smaller Than the Size of the Print Data?
Replace with paper that is the same size as the print data. Loading Paper(P. 133)
Have You Cleaned the Fixing Assembly?
These symptoms may occur when the fixing assembly is dirty. In this case, clean the fixing assembly.
Cleaning the Fixing Assembly(P. 468)
Troubleshooting
516