In ES3.1 preview,
Landscape will render default material if change landscape material by using material instance of landscape's material.
Will render correct if using another material's instance.
1.Create a simple material and it's two instances A & B
2.Create landscape using material instance A
3.Change to ES3.1 Preview
4.Select the landscape and apply material instance B to Landscape Material
5.Landscape now render default material in ES3.1 preview and render material instance B in SM5
6.Create another material and create it's instance C
7.Select the landscape and apply material instance C to Landscape Material
8.Render correct in ES3.1 preview and SM5
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-79429 in the post.