Black ink has spaces in lines, color prints fine.

Black ink has spaces in lines, color prints fine.

My Epson Stylus NX420 black ink has spaces (banding) in the lines when printed. I've replaced the cartridge 2 times, run multiple nozzle checks and head cleanings. It did not correct the problem. I also printed out a large .25" x 9" inch solid black box to find out what looks like on a larger scale. Here is a picture (or look below): http://bit.ly/2nGUwy0.