Hi, thanks for the scene. The RailClone001 object has exceeded the number of faces defined in Display->Limits
Probably the warning message is not shown because you turned on at some time the 'Do not show...' checkbox:
I just noticed RailClone doesn't show any message in General->Object Statistics
or the Lister if an error occurs in the last render. It would be caused by the Corona implementation, we'll check that.
Please not that not all segments generated by RailClone are instances. Pieces which are be bended or sliced cannot be instanced, and RC creates a mesh with all of them.
In this case, the bush segment is a high poly mesh (more than 1 mill. faces). That's is causing the limit exceeding.
As alternative, you would create a basic structure for the bush with RailClone, and scatter the leaves over it using Forest. This method may be more efficient on the instances generation.