I am currently working in Adobe Illustrator 2020, but this has happened to me since at least 2018-2019:
I will create an RGB document, create my RGB swatches (the brand colors I use are unsaturated pastel colors) and after working with the file for a while (dragging screenshots in, playing with text layout, etc...) My unsaturated pastel colors will randomly change to a hypersaturated brighter more vibrant color. It really destroys my productivity since I end up having to go back and adjust all colors before export. I never see the actual change occur, its almost as if it happens when I have the window hidden and am looking at something else. The only thing I can image that could be causing this is when I drag in screenshots since they are foreign to the document. I've attached screenshots of what the color starts as, and what it consistently changes to in all my documents.
 
 
Original Color
Distorted Color