My Windows 10 machine updated itself and since the new update, it cannot play fragmented mp4 files properly.
Here is an example file:
https://drive.google.com/file/d/0Bxyb9Iftjh4DUWdfV2JvMEs1OEU/view?usp=sharing
After you start the player, you need to seek it a few times for it to play properly. It was fine before the update.
This file plays fine in Windows 10. Please check this.