Be aware of a haze that might have formed on the print. Polish a print without gloss enhancer with just a cloth and see what happens then, apply the gloss enhancer or a varnish in a next step and check whether haze has formed again. The HP Baryte Satin showed that problem and my first comments on that paper with the Z3200 did not mention it as I was not aware of that issue then.http://www.pigment-print.com/review/Z3200FirstPage_2.htmhttp://www.pigment-print.com/review/QTRBaryteSatP.gifhttp://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/message/2123
Despite the haze I think there was also something wrong in the media preset for that paper, on the Z3100 one at least.
Do a new calibration. Try other media presets too to eliminate a flaw in the calibration or profiling step that may be related to this media preset. If no solution is found it could be that the Z spectrometer is not working correct.
The L 2.8 is very high = D 2.5 or so, L 12 is about D 1.85. That is a huge difference. The next black patches, as measured, are in line so a bad curve fitting in the calibration is unlikely (if the media preset has no influence there).
Try the B&W mode too for reference. Driver color management on + AdobeRGB set as the expected color space and Qimage's color management off then. Print a QTR 21 step greyscale target with 2.2 Gamma assigned or a neutral RGB one with AdobRGB assigned. It looks like you have a manual meter for control so you can measure the patches and linearise with QTR linearise tool. Check how linear that greyscale target was printed.
My 2 cents.
Met vriendelijke groet, Ernsthttp://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2012, 500+ inkjet media white spectral plots.