CameraActor Displays black screen when changing aspect ratio and running in Mobile Preview

I’m using a CameraActor in my map to show the view from the CameraActor on EventBeginPlay.
I referred to this thread to enable portrait mode view from my camera since I intend to run the appication on an android phone in portrait mode.
Its all working fine when I’m running the map without enabling the “Constrain aspect ratio” property of the camera actor.
But as soon as I enable the property and change the aspect ratio to 0.5625 the view is totally black when running the game.
Another important thing to note here is that this black screen issue is only occuring when running in
"Mobile Preview ES2 " mode only. When I run in normal mode (Selected Viewport or Standalone Game) it works fine and shows up the camera actor’s view in portrait mode as expected