Share your experience!
Its usually the video file is corrupted/unsupported codec or just a partial video.
Try these:
1)Test your videos on third party apps like MX Player etc to make sure the video is also playable on other apps.
Next
2)Go to Settings > Apps > Scroll down until you found "Video" > Tap on Video and tap on Clear Data,Clear Cache and Force Stop > Restart your phone and see if the problem still exist.