I'm using CRU with my ViewSonic 2458 monitor for a time now without any issue. The only thing I used that I set the freesync range to 48-143 from 48-144 because if not, there is a slight flickering in certain games. So yesterday I updated to Windows 10 (2004 version) and since then when I start my PC or switching to display port(PC) from hdmi input the whole screen turns darker. Exactly like if I go to AMD Radeon software and turn the contrast to 0. If I turn the monitor off then turn on or restart the display driver with "CRU" the issue go away but I have to do this every time I turn on my PC or switching back from hdmi. If I go back to the original range (48-144) the issue only present when switching from hdmi to display port input. After going back to the older windows build (1909) all my issues went away. So currently I don't know if its a windows update issue or the radeon software is not ready for the new windows build?
VGA: R9 290 / with latest optional radeon display driver