Tone rendering problem Epson3880 Piezo WarmNeutral P2


I have been using Piezography for almost 3 years and have been extremely happy with the results.
Now I have a problem with the tone rendering on the print. The dark tones from 75 % to 99% are printed clearly lighter than what they should. The light to middle tones are printed a little bit darker. I here attach a screenshot of my exel sheet with the measured table densities and graph. I have measured the densities from prints with my Epson 3880 on Piezography Warm Neutral P2 = 6 shades of gray. The measurements have been done with DataColor Spyder3Print. The measured values are from prints on Hahnemule Photo Rag Ultra Smooth using the corresponding curves for printing.

The nozzle check print looks perfectly fine (image attached). I also made a cleaning with Piezo Flusch according to IJM video instructions with no help.

I have not filled the ink cartridges after a previous printing with good results.

I also printed a QTR-8 Channel flush image with QTR Rip / Print Tool in calibration mode. Hahnemule Matt Fibre 200 gsm paper. The measured densities / channel are here:

K/MK/shade 1. 1.62
C/Shade 2. 1.09
M/Shade 4. 0.79
Y/PK. 0.96
LC/Shade 3. 0.94
VLM/Shade 5. 0.48
LK/Shade 6. 0.33
LLK/ Gloss Optimizer => Blank field

Is the Shade 2 and / or Shade 3 density too low?
Are these values what they should be and do they give some hint where the problem could be.

best regards Lasse

Please prints the 129 Step target and measure and upload the measurements here and I will compare/graph it again linear.