I've had the same problem. I got it resolved. When you connect soundbar to hdmi arc port, the sound bar audio delay default for some reason is set to 300. You can change that setting by hitting the setting button on your sound bar remote 3 times. It will say audio sync and you will see 300 when you press up direction on the sound bar remote (you need to press up or down button on the remote pretty fast or it will exit the sound sync menu). I've set mine to 0 and my audio on my TV to bitstream, and Dolby digital and audio delay to 0 and now everything is in sync. I hope this helps.
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