To reproduce:
1. Create terrain.
2. Add cloth component. (or any other component which would have "Edit bounds" or "Edit constraints" button)
3. Press "Edit Bounds" on Skinned Mesh Renderer (sam with "Edit Constraints" on Cloth component)
4. Scroll to the very bottom of inspector.
5. Press "Edit Bounds" on Skinned Mesh Renderer again.

Expected result: Terrain Collider's info stays in it's own box.
Actual result: Terrain Collider's info moves out of bounds.

Reproducible: 5.6.3p1, 2017.1.1f1, 2017.2.0b10
Fixed on: 2017.3.0a3

Workarounds:
Does not reproduce if "Terrain Collider" is minimized.
Or if Inspector is not scrolled to the bottom.