How to reproduce:
1. Open Unity project "PrefabBugExample2" attached to the latest users email
2. Load "MenuScene" scene
3. Enable:
* Canvas-->Main Menu Panel,
* Canvas-->Main Menu Panel-->Music Panel,
* Canvas-->Main Menu Panel-->Music Panel-->Social Panel,
* Canvas-->Main Menu Panel-->Music Panel-->Radio Panel

Expected Result: UI elements are located in the same positions as they used to be in previous versions (970914_Expected.png).
Actual Result: UI is corrupted (970914_Actual.png).

Regression first introduced in: 2018.1.0b5.
Reproducible with: 2018.1.0b6, 2018.1.0b5.
Not reproducible with: 2018.1.0b4, 2017.3.1f1, 2017.2.1p3, 2017.1.3p1, 5.6.5p1.

Note: This example project was saved in 2018.1.0b4. UI is corrupted in 2018.1.0b5 and 2018.1.0b6.