If you watch video on youtube or watch substance-material on arstation.com then you can see that all displacement-material is shown using sphere bcoz sphere object has no straight angles (90 degrees)
I try’es do use material with displacement in unreal engine and got obvious artifacts in form of gap between two part of textures.
It’s been 30 years when this problem exists and nobody could solve it.
I have made such an object
You can try to make a backend too… it is like scanning the model and obtain only one texture… i did it once in Blender using textures from sustance painter and it work perfect!!
It is also possible that the model does not have enough triangles… Unreal triangulates the models… look at the mesh properties maybe you can increase the triangles… and you can disable the LOD too (LOD removes triangles with distance)