Default Video loading problem (70%through)

So when I watch videos online through any of my android video players(video player, mx player, es video player) they will start getting laggy about 70% percent through the video. Not all videos but just about any video longe than 8 minutes.. The video is unwatchable. It plays but just skips(plays then stops over and over)... Any ideas why? My Internet speed is not the problem.

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