Epson 9900 cyan banding problem, Please help if you know how to fix it!

Hi everyone!
I'm new here and in the large format printing field.I bought my first printer about a month ago and I have an issue with it. I was wondering if anyone could help please. I bought the printer refurbished.It is old and has no guarantee (couldn't afford a new one), and now I noticed it leaves white lines when I'm printing cyan (happens only with cyan)! It also leaves a vertical white line 1 inch from the edge of the paper every time I print something. The guy who sold it to me is also a large format printers serviceman but he doesn't return my calls!!! The nozzle check looks good, and I've ran power cleaning a couple of times and print head alignment but it still keeps happening.

 

Just paid F*** $1800 for a new printhead+$500 labour for replacing it! it seems like you have to look at the nozzle check with a magnifier when you're buying a used printer. In my case there was a slight dent on the vertical lines of the nozzle check between each color which you can't probably see unless you're PRO! So this all means I was ripped off by a so called "Epson certified refurbisher" but I'm gonna think of it as an expensive lesson that I learned! "getting cheap is pretty expensive"