Something weird happens to mesh faces when I import them from blender to UE4

Hi,

I made a model of a crown in blender, then imported it in UE4, assigned some materials and PP effects and it looks garbage.

For comparison:
This is how materials should look like. Yellow, red, grey.
image

This is how they look on the crown (same materials btw)
image

Same red, same yellow material.
Why is this happening and what can I do to fix it?

I might found the problem, but I dont know what to do.
Normals in blender should be blue, that means they are flipped outside. So it looks good in UE. But in the crown case they are red.
In blender
image
Imported in UE
image

When I flip the normals in blender to make them blue, thats how the crown looks then in UE:
image

I assume that the crown has problems with materials, because the normals in blender are red and not blue.

Can anyone help please?

I fixed it by mirroring the mesh in blender. I still dont know why it worked, so if anybody knows the explanation, please share

Maybe setting the crown metal strips material to 2-sided would help?

It was two sided