I've got a couple fire sticks. They do have sync issues on occasion but seems my ISP has more to do with that than the actual app involved (or its location), but is usually easily rectified by stopping the video and playing again. Can't say any one app is a culprit at least, and use a variety via the Amazon service. Do the tv apps generally provide multich audio codecs? That was one reason I got away from my "smart" tv's apps....which were only 2ch versions and not upgradeable. With eARC I'd assume the tv can even do lossless codecs if asked?