We've had our QN90A for a week and I'm very unhappy with the audio. After about 1/2 hour of watching the audio and video is very annoyingly out of sync. I can temporarily fix it by changing the channel, but that is obviously unsat.
Firmware is current.
Please update your TV to version 1560.5 to resolve the lip sync issue. You'll need to first download the file, unzip it, load it to a USB and connect to your TV to do the update.
Download link here: https://www.samsung.com/us/support/downloads/?model=N0054535
Solution for AT&T setup box: De-select the surround sound in the options menu of the AT&T setup box, change the audio output selection to stereo. This will resolve the audio sync issue.