Tree place with terrain does not rendering shadow when tree goes out of camera field

There is my problem...

I'm making a game in VR, I've got a forest and when trees goes out of my camera field the shadow on the ground disappeared.

I did different test and this is what I get.

- I got no problem with my tree prefabs with lod (just mesh object)

- Unity tree with the "Tree" component disappeared when out of camera field and so the shadow

- But if I'm placing them without the terrain painting (just drag and drop prefab on scene) I don't have this problem (but it's gonna be a lot of pain for placing all my tree)

So I conclude the problem is from something with the terrain tree settings but I don't know what I need to do...

This are some of my configuration



If someone can help me thanks a lot ^^