I am able to reproduce the problems, but it happens with specific steps, sometimes a simple click, other times first a rectangle selected. What makes it difficult to reproduce again is the destruction of the color that happens in the library, you need to add a fresh created swatch again to make it reproducible again.
In Illustrator:
Create a new CMYK file.
Create a spot color and add it to a CC library. Close the document
Create a new CMYK file.
Just Double click a Spot Swatch in the Library, click OK.
Color gets added to the swatches as Spot (although the Color Mode has become CMYK).
Create a new CMYK file.
Draw a rectangle.
Click the Spot color in the CC library.
No color added to Swatches, color fill becomes Process.
After that the color in the Library has permanently changed.
Spots added from Illustrator show CMYK values in CC Library.
Spots added from InDesign show Lab values in CC Library (and become added to swatches as 100% magenta process color when double clicked in Illustrator).
Double click a Global CMYK Swatch in the Library.
Color gets added to the swatches as a 100% Magenta Spot color.
I have added a video to Uservoice:
https://illustrator.uservoice.com/assets/238147915/CC%20LIB%20COLORS%20PROBLEMS.mp4