- This issue is not reproducible in 2018.1.9f1, but it should be backported to 2017.4. I couldn't find the original PR.

Reproduction steps:
1. Open the attached project.
2. Switch Platform to iOS.
3. Make sure metal Graphics API is set in the Player Settings.
4. Make sure Anti Aliasing is set in the "Edit > Project Settings > Quality".
5. Build the "zhujiemian 1" scene.
- You can switch GrabPass with UI buttons on the screen.

Actual behavior:
- Skybox is rendered over other objects, light spots, and black bruises (Screenshots attached).

Reproduced with:
iOS Metal (2017.2.3p2, 2017.4.8f1)

Not reproducible with:
iOS Metal (2018.1.9f1),
MacOS Metal,
Editor Metal,
iOS GLES

Note:
- Check the attached video "iphone6s.mov" to see the actual/expected behavior comparison.