QTR-Quadtone RIP

Hi everyone - this is my first post here. I recently decided to try
out the QTR inks for printing BW prints on my Epson PHOTO 890. I have
had more than a few problems to date..  prints too light and such, but
my major problem which I cannot seem to fix is 'staircasing' or how
would you say it.. 'wiggly lines' all over the place. Now, I have
recalibrated my print heads I don't know how many times to no avail..
any suggestions?

Thanks - Bernard