Paper2D > Viewport brightness increases gradually when playin

Hello all. I have started learning unreal engine with paper 2d. I am building a tower defense game and prepared a minimal level for that. I have a pawn class that has only a orthographic camera component. This pawn looks at the level from on top.

When I hit play, I see my level through the pawn’s camera. However, as time goes by, level gets gradually brighter and brighter. I know that this is an issue with lighting but I have no light objects in the level. I created an empty level which has nothing.

I don’t know where to look for the problem. I don’t want this behavior and I don’t know how to shut it down. In addition to that, since this is a 2D game that only has sprites, I find it weird if this is an issue with lighting.

This is before and just after I hit play:

This is the image that has taken after a few seconds. It is brighter than the first image:

Thanks for the help in advance!

I have the exact same issue. Do anyone has a solution to provide ?