... I noticed that after the 70% patch, starting with the 65, the next 2 or 3 patches were abnormally lighter. Then, at 55%, they got darker again and the progression to white seemed more uniform...
It could be the cyan position ink that is too light or not set up correctly. See that the settings are as shown in the Curve Creator screen shot in the Jpeg above.
However, when I printed the Calibration Print, the grey scale for each cart looked quite uniform.
But was the cyan position significantly darker than the magenta position ink?
As an aside... do the mixed inks grow stale after a while?
They settle (as to all pigment inks) with time. It's a good idea to agitate them the night before you're going to re-load or mix a new batch. (Let the air bubble rise and too-large particles settle over night.)
Paul