Instability of CMYK color picker values

Summary:

Instability of sliders in CMYK mode / Impossible to set a CMY color value if the Black value is not equal to 100% (seems related to inkscape#2183 issue). I'm hoping that my bug report is clearly explained, if not please ask so I can complete and/or send a gif demo. Thanks 😄

Steps to reproduce:

• Open Inkscape (new document)
• Create an element (for example a rectangle)
• In the color picker, Fill Color, choose the CMYK mode
• Change the Black value to something between 0 and 99
• Click on the Cyan color field or enter a value
• Click on the Magenta color field or enter a value
• Click on the Yellow color field or enter a value

Also, from a late test :

Converting a RGB value to CMYK always set one of the values for Cyan, Magenta, or Yellow to a null value.

Same behaviour when trying to change a C, M or Y value fro 0 to something else (others cursors moves, then another value is set to null)

What happened?

When entering the third value (Yellow), the Cyan and Magenta values change randomly. This issue only occurs when CMYK mode is selected; RGB, LAB, HSV, etc. are not affected.

What should have happened?

Previously set values are retained as selected.

Version info

Inkscape 1.4.1 (1:1.4.1+202503302257+93de688d07)

                      Compile  (Run)
    GLib version:     2.80.0
    GTK version:      3.24.41 (3.24.41)
    glibmm version:   2.66.7
    gtkmm version:    3.24.9
    libxml2 version:  2.9.14
    libxslt version:  1.1.39
    Cairo version:    1.18.0 (1.18.0)
    Pango version:    1.52.1 (1.52.1)
    HarfBuzz version: 8.3.0 (8.3.0)

    OS version:       Ubuntu 24.04.2 LTS