I had this problem once and if I remember well this was cause by cross-over inks. I tried to print the same image with two different profiles from Photoshop and saw that one profile gave me far more "solarization" ( it was more a solid patch of grey looking like a tonal separation - old days).
I reprinted the QTR calibration file and looked closely where the cross-over was; then I removed the cartridge that was offending, flushed it and refilled with new ink. The problem was almost gone. I the bought QTR Print Tool, fiddled a bit with a generic profile for my paper and everything is working fine since then.
Hope this helps.