You may have to take a picture of the display rather than taking a screenshot. If the visual artifact is not in the source image then screenshots won't show it on other screens.
That said, usually gradients in dark scenes are due to color depth settings or a limitation of the display. If this is something that only appeared recently then I would check to see what color depth is being used. It could be that a recent driver update changed your display mode (and hence the color depth).
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…
