Imported plane (fbx from blender) missing faces problem.

Hi, please help me.
Im created in blender a simple plane, added some noise with displace modifier.
Then exported this fbx to unreal engine,
When UE4 imported and created tris from faces missing some random triangles.
The faces in good direction, not that the problem.
Tryed remove that faces, and create new, but missing anyway.

Somehow the displacement modifier cause the problem, but don’t know how to fix it.