OS 10.12.5
Yesterday I took 3 video clips (MP4s) and they only play normally in Quicktime.

In Elmedia, the screen is green but the audio is ok. In VLC, the clip flutters (for want of a better word) for about 5 seconds before playing normally. My default setting is VLC.
This has not happened before. I have not changed any VLC preferences.

Anyone know why VLC is acting that way?

I prefer to keep VLC as my default setting.