Black Reflection when it's blurred (Ray Tracing is OFF)

Hi, as the title says, but when the rougness is 0.0 then there is no problem, but when the roughness is 0.3 then the reflection becomes black, see the image bottom right. I’m using Unreal Engine 4.24, I was migrating from 4.22 to 4.24 and the original project has no problem but when I duplicate the project then a problem happen.

Scene information on the bottom image (Unreal Engine 4.24):

  • There is a Sphere Reflection Capture and I already build all reflection captures.
  • There is a glossy Sphere with a black reflection when its roughness is 0.3

Please help, I feel so sad because I cannot come back to Unreal Engine 4.22 anymore, backward compatibility is not possible, I explained that even if I duplicate the project then problem. My real problem is I want to create a new project by duplicating the good project and delete all objects, but it doesn’t work.

No one found a fix for that bug, but I found a difficult solution:

  • Create a new project.
  • Test if the blurry reflection is okay, and it’s very probably okay with the new project.
  • Copy all the objects from the old project to the new project.

You may wonder why I wrote these, because most of the time I will forget the solution in the future and here is a help for myself in the future.

Think it has something to do with backface culling, or depth / sort priority? Another user posted about certain refractive glass materials in their project having black splotches, with one becoming almost entirely black. Those were heavier refraction based glass materials, one of which is a sphere for testing. Higher roughness might be mixing reflectivity of other things in the scene more than it really would when working correctly. Like spreading the black surfaces from nearby further along that sphere’s roughness=0.3 surface.