This occurs if the toner wax remaining on the fusing belt is uneven.
This may occur if:
Paper with a thickness equivalent to Paper Weight 7 or 8 is used, so that the required temperature is high
Slippery paper is used
Translucent paper is used
Cast coated paper is used
A solid image with a high image area ratio is printed
To adjust the following settings, pre-register the type of paper in use as a custom paper. For details about registering custom papers, see "Specifying a Custom Paper", Preparation.