Windowed Fullscreen causes Lighting Variations in Rendered Envrionment

When a scene is light with a single Stationary Directional Light and a Single Stationary Skylight and packaged to use Windowed Fullscreen, there is a difference in how the scene is rendered compared to a normal Windowed Version or Fullscreen version of the scene.

Fullscreen (matches PIE and in Editor Rendering):
[Image Removed]

Windowed Fullscreen:
[Image Removed]

Issue has been reproduced in 4.11 Preview 2 and in 4.12 Dev-Rendering-CL-2822902

Packaged Windowed Fullscreen and Fullscreen Version can be downloaded [Link Removed]

1. Open the attached Project
2. Package for Windows 64 bit
3. Ensure that the GameUserSettings.ini file in the packaged content is set to:

   [/Script/Engine.GameUserSettings]
   Version=5
   AudioQualityLevel=0
   bUseVSync=False
   ResolutionSizeX=1920  (match your monitor's resolution)
   ResolutionSizeY=1200  (match your monitor's resolution)
   LastUserConfirmedResolutionSizeX=1920  (match your monitor's resolution)
   LastUserConfirmedResolutionSizeY=1200  (match your monitor's resolution)
   WindowPosX=-1
   WindowPosY=-1
   bUseDesktopResolutionForFullscreen=True
   FullscreenMode=1
   LastConfirmedFullscreenMode=1
   

4. Play Packaged Project while Editor is open

RESULTS: Windowed Fullscreen is rendering differently than Editor and PIE

EXPECTED: They should look identical.