Manually made base curve according to instructions is deformed

Hello guys,

I stumbled upon the Darktable and would like to give it a try to process photos of art pieces such as paintings.

The predefined base curves for Nikon Cameras produce much different results in comparison to my Nikon’s D3100 JPEGs.

Manually made base curve looks horrible even-though I think I followed all instructions correctly. ( and video below)

I took images using Let’s Build Our Own Basecurves by harry durgin
(meaning 3 images per one “stop” - images here)

Processed them like this
for each raw in the folder do darktable-curve-tool-helper -s “NIKON-D3100-100.dat” “raw”
after that darktable-curve-tool -s “NIKON-D3100-100.dat” -z -e “one-of-raws” -n 16 >
script if you wish

Computed curves are deformed pdfs

Can you please suggest any hints to make it work?

Thanks in advance!