Vertical lines when printing

I am printing a big run with a lot of solid red and or black, both of the samples attached are from 2 different HP 360 latex printers, do you know what is causing the line down the print?

from what I've been reading on other topics about the same issue, it could be a plastizer problem. A lot of banner materials have a short shelf life compared to others.. The plasticizer comes out of the media, and causes the latex to flow away from where it should be. One tech suggested to clean an area of the substrate with (alcohol I think), to see if it helped. A lot of people noticed that the area that was cleaned printed fine, and the untouched areas till had the lines in the print. If this fixes the print, you may have to wipe down the length of material you are going to use before printing.. time waster, but may work! see if it helps!