Smudge Marks Appear on the Back Side of Printouts

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
Does staining occur when you print photos or other halftone images on small-sized heavy paper?
Setting [Rdc. Tnr Flaking from Heavy Sml. Ppr] to [On] may solve the problem.
[Home] screen on the control panel [Menu] [Adjustment/Maintenance] [Adjust Image Quality] [Special Processing] [Special Paper Processing] [Rdc. Tnr Flaking from Heavy Sml. Ppr] [On]
* Specifying [On] may make printing slower.
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