Imported mp4 videos are halfway playing and then cut to black for the duration of the video iMovie 13/Quicktime

I'm using Nvidia Shadowplay to capture gamplay and it is outputting the video as mp4 and it plays perfectly in Windows Media Player and VLC (Both on Mac and Windows). However, when I try to play the video from Quicktime or import it straight to iMovie it will play the video for about two or three minutes and then the last 10 or so minutes are being cut off and replaced with black video output and no audio. So far my solution is to upload the video to Youtube and then download the video. iMovie should be able to play mp4 videos fine because when I play the same videos downloaded from Youtube, they'll play perfectly fine.

This is iMovie 13 by the way.