There is a problem with black developer so it will be better to replace the black developer housing and the black developer material. I hope that you use original Xerox toner.
I did the printing tests, color calibration and everything, the most serious error is this, besides that it prints a lot of banding
Thank you for using the Support Forum. Please take a look at the online article about "foggy" background and follow the possible solutions listed there. If those solutions do not help please consider contacting your support centre for further assistance.
I have a problem with my xerox7800 it always prints a gray layer, this gray layer alters the colors and there is an excess grain, it feels like it loses a lot of quality and there are usually spots too
I have no idea what it could be.