I use a new Xerox VersaLink C7000, only one month old. And i have a problem especially when printing in the optimized or photo mode.
Some colors are printed very streaky. The problem is worst with light colors, or is most noticeable there. Strangely enough not all colors are affected. I have carried out various tests with different colors and papers. Other papers make no difference. And it makes no difference to set a color value to zero, for example Y=0. The printer is new, therefore I exclude a mistake with the hardware or consumables.
I have attached a photo. The two circles on the upper part are printed in standard mode (little streaky), the two circles on the lower part are printed in optimized mode (very streaky).