Hello, phountain.
Welcome to Microsoft Community.
I have some ideas.
Have you tried copying the file to another computer for playback testing?
Can you share the file extension of the problematic file?
Is it an H265 video?
This might be due to video codec issues.
Additionally, you can also try other video playback programs, such as third-party media players.
Thank you for your cooperation.
If there are any updates, please feel free to reply.
Best regards.
Malygos - MSFT | Microsoft Community Support Specialist