Hello Chris,
Ideally you would also need to give an indication as to the source of the file as this would have a great influence on the end result, i.e. if you are streaming wirelessly, via wired network, NFS, SMB, as well as the full detail of any and all hardware between the source and the Mede8er etc... (cables, routers, switches, wives...)
The more detail the better - please also provide any troubleshooting you have tried so far as well as the results i.e. have you tried placing the file on a flash drive and playing it from there, etc...
If the situation doesn't improve by changing the source of the media file then I would ask that you provide a sample of this movie with the sound issue to the FTP address as discussed
here?
Please provide the exact time within the movie that this issue presents itself as well as any necessary steps one would need to take to recreate your issue so that this can be looked into.