Here is the xmp… around -120 or +120 as you use the scroll wheel it will jump to black and then back the next rotation of the scroll wheel. If you move the purity slider one tick the color comes back… Its extreme and not something you would likely do as things seem out of gamut at that point but maybe it points a small math thing… also when you right-click the slider and select a negative value it jumps to the positive one initially and the reverse…
XT30hSLI00100NR1.RAF.xmp (20.3 KB)
Window 10 for this one and older 745 Nvidia card but my machine at home was much newer and I think I saw something similar… just quick messing around… as I said I will try to be systematic at home later and maybe its just a case of pushing things to weird extremes…