VRay rendering Tiles material problem


I am trying to set up a Tiles material.
I set up the the Tiles Count and Mortar Gap to suit my needs.

Then run a render:

On start, tiles look as intended (“building light cache” phase)

then when it comes to “rendering image” it is like there is only very big tiles…

Another one between the to phase of render (and without the tree texture):

Any thought?