C32HG70 here. It did it when I used FreeSync on a Vega64 and it's still doing it with an NVIDIA GPU. Just curious if it's a problem with my monitor or if others have had this issue. It's very easy to see in NVIDIA's pendulum demo with Show Test Pattern enabled as the background will flash back and forth from dark to light gray. Standard Engine doesn't seem to have any issues, but of course it also has a much reduced range.