Problem with Skylight and metallic materials. This did not happen in Preview 2.
Create new Level -> Default.
Place a sphere in the level.
Create a new Material, set Roughness to 0 and Metal to 1, apply it to the sphere.
When playing in a new window, the sphere is almost black, when playing in the viewport it works.
This somehow seems to be related to the Skylight and metallic materials. When changing the Skylight mobility, the sphere appearance also changes.