Exported OBJ file gets slightly ditorted UV.

When I export an object as OBJ file, its UV gets slightly distorted.
It’s only a bit, but it caused a problem when I was painting exported mesh with 3D-COAT.
Is this how OBJ works? Or is it just a bug?

I’ve attached the screen shots of UV layout from original mesh and exported and imported mesh.
I also attached the .blend file.

I’m using blender 2.78a.
I hope someone knows the solution to this.
I currently use FBX. It works just fine.

Thank you.

Attachments



UV_test.blend (5.5 MB)