Speaking of corruption, I found this[1] video a while back. On mobile the video shows up fine, but on desktop it's just a gray screen, although the thumbnails work.
I can confirm that the mp4 I downloaded is not (detectably by my desktop video player) corrupt. I am not sure what it is, but it is not corrupt. (Except for the filename, but that is because javascript is brain-damaged as regards strings.)
[1]: https://www.youtube.com/watch?v=lOb8TNn7sDE