Digital BW, The Print

I'm trying to create some curves (in QTR) for Epson Glossy and 
Semigloss for my 1290s, but can't get rid of a vertical banding
pattern (that is to say - in the same direction as the printer head 
motion) which is showing up on the initial 100% Ink Pattern Page (in 
calibration mode.) I've not seen this when printing to Matte paper, 
and have tried numerous head alignment operations. Also tried
different settings in QTR; speed, resolution and dithers.

Anybody out there got any ideas or solutions?

regards, Jamie Creed