I am seeing horizontal lines in 50% test page for Cyan that the spacing doesnt match up to anything in the repeating defects page. Any suggestions as to what may cause this?
If it only happens with CYAN, you would need to look to the imaging unit, you may be able to swap the Cyan one with another color (like Magenta or Yellow) and if the defect changes to that color, you would know it was the Imaging unit.
Oddly, the supplies for this machine implies you can't swap them (Neutral until installed), while you can in most devices, but give it a try because they are not cheap, you do not want to just throw money at the issue
It could be, but I am not a hardware expert by any means, no idea if you can test a developer or not.