Need Help Printhead Manifold

We have a WorkJet Eco Solvent 4-color printer that recently stopped printing one complete block of the two blocks of Cyan and of Magenta on the second head when printing a head test. We replaced the dampers, and used a syringe to check for air leaks, but that didn't resolve it. Then by switching the Black ink with the Cyan ink on that head, we determined that the problem wasn't with the dampers, as that same block of Black ink then stopped printing.

So it seems that it would almost have to be a problem with the print head or the manifold. We next bypassed the ink tanks and ran some UV solvent through the print head hoping to clear up any clogs. We have also let the print head soak overnight, but the problem still exists.

How often do the manifolds need to be replaced? Is there an easy way to check to see if it is leaking and/or clogged. Since there is about a 10x price difference between the manifold and the printhead, any advice that would help us understand how to proceed would be greatly appreciated!