Steps to reproduce:

1. Download and import attached project. (CameraPreview_Strip.zip)
2. Open scene: Classic_E06_F01
3. Select camera and inspect its preview in scene window.
4. Switch to Game view and then back to Scene view.
5. Select the same camera.

Expected result: Nothing changes.
Actual result: Camera preview have changed. It looks like it lost depth test (objects further from camera are drawn on top of objects closer to camera)

Reproduced on: 5.4.0b12, 5.3.4p2, 5.2.4f1, 5.1.4f1