Sorry this has not been answered
Can you post a screenshot of what you’re seeing when it “goes gray”?
I can replicate what you described if I activate the mask in the adjustment brush, and then choose to have it affect the unselected area. If you uncheck the mask the problem will go away. Or you can change the behavior of the mask.
Thanks for getting back to me.
I tried what you explained but had no success but what I have noticed is if I put a value, say in the exposure slider, then it works. I have never had to put a value in before ( everything set to zero ) I just paint the area and use the slider to set the effect I require.