hello Jean
sorry for my late answer
I just tried your file and very quickly, the problem appears also . suddenly it works and suddenly it doesn't work anymore.
in fact, if I select an object, I open the color palette, I select a color, then the color is applied immediately to the object BUT, as soon as my cursor leaves the contour of the palette, the object resumes its initial color (see photo)
as you can see in the photo of my screen; the object is blue whereas I have just selected it in light orange. it turned blue again as soon as my cursor left the palette!!
help this is a real problem
François