Cause
When toner which is used for a previous job remains on the fuser belt, a wax substance from the toner adheres to the fuser belt surface, and then applies more glossiness to an image. This causes different glossiness between an area with much glossiness and an area with less glossiness (interleaf, top/bottom margins, no image area, etc.).
This is likely to occur if:
Using thin coated paper which is the paper weight 2, 3 and 4
Printing a solid image with high coverage
