Steps to reproduce:

1. Open Unity;
2. Open attached project and "test.unity" scene;
3. Notice that in the scene there is Terrain gameobject with assigned "New Terrain 1" asset file;
4. Select Terrain gameobject in the Hierarchy view;
5. Notice that transform gizmos in the scene view are displayed in the center of Terrain (relatively to gameobject);
6. Open Project tab;
7. Delete "New Terrain 1" terrain asset file;
8. Select Terrain GO in the Hierarchy view;
9. In the Inspector tab assign "New Terrain 2" asset file to the Terrain gameobject;
10. Select Terrain gameobject in the Hierarchy view;
11. Observe transform gizmos.

Actual result:
Transform gizmos are displayed in the corner of terrain (see attached actual.png screenshot).
Also see attached gif video for full scenario.

Expected result:
Transform gizmos should always be displayed in the center of Terrain gameobject to preserve consistency within the product. (for both adding and re-assigning Terrain gameobject). See attached expected.ong screenshot.
The expected behavior could be derived from Plane gameobject - its gizmos are always displayed in the center of the plane.

Reproduces in 5.3.0b5, 5.2.2p2, 5.0.0f4.
The issue has different behavior in OSX and Windows - see Notes below.

Notes:
- For Windows (8.1) gizmos position is always in the corner of Terrain - when either adding and re-assigning asset file, which is a bug.
- For OSX (10.11) gizmos are in the center of terrain when adding it and in the corner when re-assigning asset file.