QTR-Quadtone RIP

Hello,

I have been following the group for a while and this is my first post.  I am using a slightly refurbished Epson 7600 (replaced the dampers, capping station, and cleaning squeegee a few weeks ago) with the Piezography K7 Neutral ink set.  Using Quadtone RIP, I have been getting a banding issue in the midtones.

I have run nozzle checks that all come out clean, I have soaked the head in PiezoFlush as well run numerous cleaning cycles and repeated nozzle checks just to make sure, but for some reason I still get banding.  I have used several papers from Epson Enhanced Matte to Hahnemuhle Photo Rag all with the same issue. 

Has anyone else run in to this issue and if so, what did you do to correct it?

Thanks!