Animation from blender | Normal issue

Hi all,
I have a strange issue with normals inside a FBX animation I did with blender. I don’t know if it’s related to blender export settings or unreal import settings, but here is a simple rigged animation.
The animation consist in scaling some boxes : the 1st one goes from 0.01 to 1, the 3rd one goes from 1 to 0.01 (the 2d one has no keyframe).
You can clearly see an issue with the first box about its normals. I can’t figure how to solve it : I tried multiple export/import settings with no luck.
Is someone has an idea?
You can see animation in action here :

Thanks for your help,

You sure they are all using the same material in the editor?

Probably an issue in blender

You could just delete box 1, copy box 3, move box 3 in place of box 1, reverse the keyframes in the animation graph or dopesheet and export again with the very same settings and see if it was an issue with normals or not.