I assayed this on my office PC and my private PC, however the problem has occurring both system and both is Win.
I attached other image. I have created entire new simple scene, and then I placed box and one directional light, and finally placed player start point.
Of course I could turn off all post process or some other thing including affect to view in edit mode.
But when I enter the Play mode, I have realized same tonemapping problem, and then I couldn’t fix it by full zero setting PostProcessing Volume…
That is just same situation with customized scene:(
I need clear advice from EPIC.
.