Thumbnails Get Much Darker With Forward Shading Enabled

The real time thumbnails are much darker when using forward shading in the editor. You have to open or edit an asset so that the thumbnail updates after enabling forward shading to see the effect. Also, while testing I noticed that if you disable real-time thumbnails prior to changing to forward shading the thumbnails will become black.

1. Open a blank project
2. Duplicate the cube static mesh found in EngineContent>BasicShapes to the content folder
3. Enable Forward Shading in the project settings and restart editor
4. When the editor has reloaded open the static mesh in the static mesh editor

RESULT
The thumbnail will update and will become much darker. User Reported Black thumbnails in their case.

EXPECTED
The thumbnail updates with the mesh still clearly visible.

Thumbnail turns black in forward rendering

Engine is dropping thumbnails

Thumbnail turns black in forward rendering