Audio sync issue using Serviio to xbox

I have many mp4 files that play fine on a Mac laptop and desktop machine. While Serviio appears to operating as it should, when these files are served to my xbox360, the audio becomes increasingly out of sync as the file plays, i.e. in sync at the beginning but out of sync at the end of the file. I'm not savvy enough to know where the problem is: file? xbox? Serviio? codec? Any assistance would be greatly appreciated.

[zip]

might be slow network