Some devices are not powerful enough to play certain types of movies in the context of the Unity game engine. To make sure videos play smoothly, please make sure there are enough keyframes (one every 1-3 seconds). The video provided with this case has keyframe intervals of up to 10 seconds, making seeking operations quite costly.

Additionally, the VideoPlayer settings in the project have the "skip on drop" option enabled, meaning any sync discrepancy will be compensated for by trying to seek ahead. But with keyframe intervals being as wide as described above, this operation could turn out to trigger the domino effect that makes the VideoPlayer unable to catch up. Turning this setting off will disable this behaviour and provide smooth playback (at the cost of possible desync with animations or audio over long periods of time).

One final note is that the ability to play a video smoothly is conditional to the game iteration rate to be comfortably higher than the played video. In this case, the video is 30fps, so the game should be able to run at this frame rate without any hiccups, or else the longer iteration times will prevent the VideoPlayer from consuming enough frames per second to preserve sync.