Steps to repro:

1. Open Unity;
2. Create new project;
3. Add Terrain gameobject (GameObject -> 3D Object -> Terrain);
4. In the Terrain component select Raise/Lower Terrain tab;
5. Choose 4th brush (with sharp edges);
6. Raycast on terrain and observe that brush is rendered normally and raycasting works;
7. Click right mouse button on Inspector tab and choose Add tab -> Inspector;
8. Raycast on terrain;
9. Observe the brush rendering.

Actual result:
The brush rendering is broken - it consists of 2 'nested' brushes now, the internal (dark) one is a real brush which changes upon toggling brush size in Inspector. Overall it looks like 2 brushes overlapping each other are rendered and active. This creates problems with raycasting and it stops functioning as expected. See attached gif video and actual.png screenshot.

Regression introduced in Version 5.5.0a3.

Workaround is to either switch to default layout or disable second Inspector component (doesn't work effectively).

Expected result:
Only one Inspector should be taken into account internally when painting on terrain; second Inspector tab should just reflect changes to the first one. See attached expected.png screenshot.

Notes:
- Reproducible in 5.6.0a1 (trunk) 5.5.0b6, 5.5.0b5, 5.5.0a3;
- Not reproducible in 5.5.0a2, 5.4.0f3;
- Reproducible on both Windows 10 and OSX 10.11.6.