QTR-Quadtone RIP

I'm printing on EPSG with Daniel Staver's PKN-GLOP curves and getting 
very fine lines in shadow areas. I'm printing on an Epson 2100 with 
MIS UT inks (and using PKN obviously).

I believe the banding is present throughout the print but only 
visible in shadow areas. So the net effect is a very fine, almost 
scratch like pattern of horizontal lines that are parallel to the 
movement of the print head and appearing in the deep shadows.

Print head nozzle checks are consistently fine (although cannot check 
the Y obviously as it has GLOP). I've tried reducing the ink limit of 
the GLOP but this has no effect. 

I've seen this now with two different images and am stumped. Does 
this ring any bells for anyone?

Printing tiff files processed out of Qimage and using 1440 
better/ordered in QTR. Not running absolutely latest version of the 
GUI - I think 2.2 f for QTR and 2.3.? for the GUI...

Best,

Dave Meddings