That happens when I try to play 1080p videos. I'm not exactly sure. Try this method.
"If you're having trouble with your high definition videos and they're encoded with the H.264 codec then you might want to try this: Preferences -> (tab) Input / Codecs -> (tab) Other codecs -> FFmpeg -> (tick "Advanced options" box) in the drop-list next to "Skip the loop filter for H.264 decoding" select "All", save and restart VLC."