MP4 stream not found

I'm running AMS 5 on Windows Server 2012. 

Some of my VOD MP4 videos play just fine, while others will not play and return a "stream not found" error in the player.  All videos were recorded in the same way.

The videos that do play tend to be smaller in size (<1MB), but small size doesn't guarantee that they will play.

Any ideas?  Thanks!