The problem also arose with our content. We have given an answer. Maybe this will help you too.
This problem is related to the latest Unreal Engine updates and the change in the work in mipgen. To solve the problem, select all textures. Open texture properties via the properties matrix. Go to the Level of Detail section and set the “Mip Gen Settings” parameter to “FromTextureGroup”.
More details about the solution of the problem in the screenshots:
