Mrgood's suggestion of going to a sealed ink bag bulk system is good advise (or going to cartridges).
Open ink systems get some contamination in ALL the ink colors and also get additional gas in the inks. Open systems also introduce pressure issues and problems. When inks are produced they are run in a vacuum machine which is known as de-gassing. They are then packaged. When they from that point never come out of an ink bag the inks are never exposed to air in any way so zero possibilities of contamination, and no gasses (air) can be introduced. In an open tank - there is air above the ink. When you spill some ink what happens to it, literally within minutes? As it is exposed to air the solvents evaporate out and it begins to cure immediately. if you think that does not happen at all in an open ink tank type bulk setup you should rethink things. On the issues with pressures - as an ink bag collapses it just empties out and all is good and this is the same with cartridges or sealed ink bag type bulk setups. With any type of open bulk setup it is inevitable that as the levels go up and down, floats like some setups use move up and down, the physical location of the tanks, etc ALL cause fluctuations in the pressures in the ink system. That being said if a machine was designed from the manufacturer with an open style bulk system than those issues were accounted for and engineered into the system by the manufacturer of the machine.
Aside from that I agree 100% with the others. In my 15 or so years of running wide format solvent ink machines with epson heads, if a channel starts misting like that, 95% or better odds that the printhead is simply worn out and needs to be replaced. Sometimes a head just does not last as long as others too which can be due to slightly lower quality head from manufacturing to slightly thicker ink viscosity which means the head has to work much harder to jet the ink. The thicker viscosity is generally due to lower quality aftermarket inks, ink exposure to air in open type bulk ink systems, and ink that is gone past its ideal date to be used by.
