Displacement map reprojection issue

I reprojected from high to low a diffuse, normal, and displacement map. 

The displacement map has something like a grid as a layer underneath when I use texture reprojection. 

The low-poly is just a square plane triangulated. The mesh contains two triangles.

The resulting map looks like multiple times divided and triangulated with projecting errors on the edges.

This is what I get from RC:

 

I am wondering what I do wrong. I have a mainstreamed workflow and this happens the first time to me.

 

Not sure, but i have errors sometimes, if there are not enough polygons, so maybe try more Polygons and reduce size of the mesh in other programm.

I have no idea, but I hope it might help anyway.

Unfortunately, there is no difference. 

 

Sorry then I have no other idea but to start all over again.
Or you have to wait for an official answer from CR staff.

I don’t use displacement, but have you ever tried if the highpoly map is “good”? And then use another program to reproject the textures to a lowpoly? I use Blender for such things.