Reproduction steps:
1. Open the attached project(Assets folder only, put it into another folder).
2. Play the "BadUIShadow" scene in the editor.
3. Notice that cube drops shadows(Picture attached).
4. Build and run this scene for iOS.
5. Notice that cube doesn't drop shadows(Picture attached).

Reproduced with:
* iPad Air 2 9.3.2
- 5.3.6p6
- 5.4.1p3
- 5.5.0b6 ( Unrelated crash on build )

* Samsung Galaxy S7 Android 6.0.1; Motorola Moto G Android 5.1
- 5.4.1p4

Not reproducible with:
* OSX standalone