Video glitches when rendering mode is set to "Material Override".

Steps to repro:
1. Open attached project > Open "Material Override" scene.
2. Enter Play mode > Hit Play Button[GUI Play Button].
3. Observe that video glitches.

Expected Result:
The video should work properly without any glitches.

Reproducible on:
2018.1.0b1, 2018.1.0a7, 2018.1.0a6.

Works fine on:
2018.1.0a5, 2018.1.0a4, 2017.3.0f3.

Environment:
Occurring only on MAC.

Note: Able to see glitches in the video, deactivate Rotator.cs which is attached to VideoCube gameobject.