Landscape Heightmap on Static Mesh

Hi all,
I created a Landscape and I exported the heightmap to create a mesh in blender to use as a “fake landscape” to use for long distances when streaming levels are unloaded. The idea is to place it just a bit under the real landscape but I have a problem.
When I use the heightmap in Blender on a plane and I import it in UE4 it happens that the shape of the mesh does not correspond to the shape of the landscape. It seems that the top and bottom parts in height are right but in the middle it’s kind of stretched.
In Blender I used the heightmap in Displacement modifier with strenght = 1.

How could I solve this? Is there something I did wrong?
Thanks.