The ColorMunki, and all the Epson and other third-party supplied profiles have a specified rendering intent of Perceptual, not Relative Colormetric.
When printing either as relative or perceptual from a native perceptual profile, the colors are correct and there is no sudden jump in gradation patterns. ("C" in the above case.)
When printing with the paid profile (which is native relative instead), using a perceptual intent works fine (no banding; smooth gradations; proper color) but when selecting relative colormetric during printing, the banding and off colors appear.
I'll admit to not completely understanding why relative/relative doesn't work, so if someone would care to explain, I'm eager to learn.
Meanwhile, I'll ask the supplier of the paid profiles to re-do them with a perceptual intent.
Thanks, folks.