My Q90R is also doing this through eARC. Audio is milliseconds off from video when everything is plugged into the One Connect box and passing through audio through eARC to Marantz 6014 receiver. I got so annoyed by the delay I had to connect all my devices back to my receiver and works perfectly. So now I can’t use the 120Hz on HDMI 4 for my Xbox Series X due to delay and because of this because of no HDMI 2.1 eARC on Q90R One Connect Box
I have the same thing on my series X, it's running into my LG C9 then through to a Denon receiver via EARC. Slight audio delay most noticeable on cut scenes with characters talking. Can't resolve as changing the audio delay on the reciever then puts everything else out that I have coming from the TV!
Getting the same issue. Series X is sending audio/video to my Q8FN via HDMI, and then audio to AV receiver via ARC. All sound formats have noticeable delay, except for stereo. Latest firmware (downloaded from Samsung website, applied via USB), but no luck