Would you mind sending the video to firstname.lastname@example.org? We've received one other report of Hype on Sierra producing corrupt videos, so I'd like to see if this could be the same issue.
If you can, please also send a full system profile:
1. Go to the Apple Menu, choose "About This Mac"
2. Click the System Report... button and the System Information app will launch
3. Make sure it is showing the Full information - If the File menu shows "Show More Information" choose that, otherwise you're good
4. Choose 'File > Save' to save it somewhere (like your desktop), and then attach this file to the email
In the other case, restarting the computer and re-exporting temporarily solved the problem.