To reproduce:
1. Create a new project;
2. Create a Slider: GameObject > UI > Slider;
3. Create a Prefab out of the Canvas.

Expected result: Handle and Fill of the Slider does not change their position after making the Canvas prefab.
Actual result: Sliders Handle and Fill changes their position after making the Canvas prefab.

Reproduced on versions: 2017.3.0b5, 2017.3.0b10.
Not reproduced on versions: 2017.2.0p2, 2017.3.0b4, 2018.1.0a5.