QTR-Quadtone RIP

I'm using MIS Pro inks in an Epson 4000.  Recently I've noticed white horizontal banding less 
than 1mm apart in my B&W QTR images.  I'm printing on Crane Silver Rag at 2880, 
unidirectional with PK black.  It also happens on matte papers with MK.  I've done a "puddle 
clean" with Windex, cleaned the wiper arm and the surface of the print head.  I then did 
several control panel print head alignments.  I now get a perfect nozzle check pattern 
(examined with a loupe), but the lines are still there.  I think I need to change the paper feed 
adjustment.  Does anyone know if there is a way to do that in QTR?

When I print the same image using the Epson driver with the paper feed adjustment at zero 
(default) no white lines are present.

Don