Since posting this question back in July, I’ve replaced the capping station, flushing box and dampers, and run numerous alignments, but the problem still persists. I’ve continued printing as most images don’t seem to be affected, but anything with large areas of red still show the bleed effect as in my images above. The test patterns still look the same, with the horizontal lines displaced vertically in the VM channel; this is what a test print from a file looks like. The image is red (#990000); the bleeding effect from the VM channel is obvious.
So, does anyone have an opinion about whether this is fixable, or is it terminal? Has anyone had a print head exhibiting similar symptoms?