Xvid sound out of sync

The problem is that all xvid audio gets out of sync. This doesn't happened with mkv files at all. Only xvid but also every single xvid I've tried.

When I fast forward the video starts in some kind of slow motion and it takes between 5 and 20 seconds for the video to catch up with the sound. This also happens when I'm watching a xvid. 90% of the time it synced but from nowhere the unsynced audio is there and you can see the video is catching up as it goes along.

I've tried to play with WIFI, LAN and USB. I've tried to factory reset the machine and every setting I can find.

It's the same problem how ever I do. This is a big matter because alot of things that my gf watches is in xvid.