To be honest, after owning the Shield for half a year, I can say it's without doubt the worst media player I have ever owned. Both Kodi and SMBC are just as bad, same with Plex. There are so many issues with audio sync, refresh rate changes, audio passthrough, etc
Try skipping forward a few seconds. That usually helps a bit here, but there's always still a slight annoying mismatch on sync. I just cant be bothered having to manually adjust sync on every file, sigh. And it seems to be slightly variable, which I suspect might be related to the bitstream rate (total data throughput) on the video file. I am definitively observing more sync problems on higher resolutions and higher bitrates than on i.e. 720p stuff.
Yes I do realize there are probably many of you who never have any problems like those mentioned. You might be using the speakers on your TV, or you're using the headphones output on the controller. But many (most?) people using an external audio receiver are always having problems of all kinds, it seems.
I have a Logitech Z-55000 receiver, which is perfectly capable of receiving passthrough audio from literally every media player and computer I've owned, ranging from cheapo 10 euro USB sound cards, to digital TV decoders. But the Shield is simply incapable of outputting a consistent and stable audio and video stream every time you want to use it to play a movie. There's always something that fucks up. Either refresh rate is wrong, or audio is out of sync, or there's a black screen, or no audio passthrough. And I have to keep on toggling passthrough in Kodi/SMBC settings to get it to work, and restarting the video playback.