I am having this issue with my Versalink C7000... (see photo) and have replaced the transfer belt, waste toner cartridge, and swapped out the cyan for the yellow drums and toner cartridges... still leavign blue and red... what is the developer housing unit? is it a consumable part I can order and replace as I'm the onsite DCA or do i have to place a tier 2 service call??
If you assuming a very well cleaning of the printhead lenses, it remains a problem from yhe Developer Housing (who can have some debris on developer material) and it means you need a tech to replace Developer material or even Developer Housing plus Developer material.
My Xerox Phaser 7800 is printing white streaks in Cyan only. I have cleaned all the printhead lenses and replaced the Cyan imaging unit with no help. I'm at a loss for what to do next.