QTR-Quadtone RIP

Hi All--

I just bought a used R1900 and have started working with QTR, primarily for digital negatives. I've run a cleaning cycle and a head check. Everything looks good. 

But when I try printing the ink separation test image on Pictorico, there is very visible micro-banding, in Ink 1 (is this MK or PK?) even at the 2880 DPI setting. This is especially visible at the 5% and 10% ink levels. All the other inks seem to print OK, even at very low ink levels.

Has anyone else seen this same thing? Is it a bug in QTR, or a "feature" of the R1900, or just a function of that particular black ink? Cartridges are 3/4 full, and < 1 year old.

Would I be better off using the other black as a "light black" (since it is a little less dense) to keep this from appearing?

Ideally, I'd like to use both blacks at full strength to get as much density in the negative as possible, but I'd rather avoid the micro-banding.

Any thoughts/help is appreciated.

--Greg