Repro steps:

1. Open attached projects "TestScene" scene
2. Enter Play mode and see that the animation plays
3. Exit Play mode
4. Click on the "Quad" in the Hierarchy windows
5. In the Inspector windows, Video Player component change the "Playback Speed" to 3 or more
6. Enter Play mode

Expected result: The video plays 3 times faster
Actual result: The video stutters

Fixed in: 2018.3.0a1

Reproduced with: 2018.1.0a2, 2017.3.0b7, 2017.2.0p1, 2017.1.2p2, 2017.1.0b4, 5.6.1f1,
Did not reproduce on: 5.5.3p3 (No "Video Playback" component)

Note:
Due to limitations the video still stutters, though it was minimized as much as possible