I've been noticing this for the HSV sliders in the pallette window. Let's say I set the S to a value of 40. I click on a different color to edit that, and then come back to see it is 39. Is this any clearer? I can take screen shots to show you if I'm doing a bad job of describing it to you.
This happens for all of the Sliders in HSV, but I don't know if it does for RGB.
Also, my version is 3.5.8. if that is of any help. I think it'd be a good idea to see what version PDNnoob is using as well