It actually looks like the issue might be length of model vs max triangles. The model on the left is shorter than the one on the right. I made the right model as tall at it needed to be (4ft) but I believe the number of triangles maxes out which prevents the material displacing properly.
Is there a way around this other than just adjusting the max triangles setting? I could see similar files running into the same issue: long tree branches, large paved roads, etc.
