Scroll down to #12 to see the resolution.
I have just updated to 4.12.2 n check if the video background would work in the standalone game.
I added an UMG for my game which includes a video background and a menu, the whole thing works in Editor preview but everything is black in Standalone game in 4.12.0. In 4.12.2, everything is also visible in Editor preview. But in Standalone game, the menu is visible but the video still stays black.
Are there any other ways to fix this?