7600 faint vertical lines

I have an Epson 7600 I am trying to bringing back to life. After I bought it from previous owner it has been cleaned and stored for a longer period with piezoflush. Now starting up the printer I have inserted K7 piezography inks, done thorough cleaning, nozzle checks, head alignments, platen gap adjustments, paper feed adjustments, suction, tried different papers etc…but I can’t get rid of lines/“shadows” running in the paper feed direction (vertical from top to bottom of the print). They are easily seen in the middle tones and areas with smooth transitions. I´v enclosed a couple of pictures to demonstrate.

Any feedback on this would be highly appreciated.