Can't export certain .MP4, totally random

So I've googled this issue extensively and have seen many complaints about this without having come across a solution that worked for me.

I've been importig several videos which I have shot with my phone camera (one+), edited them with presets and tried to save them/export them to my device.

Some export just fine, others fail. There's no real distinction as all clips have been made with my camera.

I've tried logging in and out as well as clearing cache.

The program doesn't give you any clues as to why this is happening, it just tells you it fails. Pretty disappointed in the app having such an issue.