I can confirm that disabling DRC or any audio improvements module or disabling Dolby audio doesn't solve the issue and still results in very bad audio quality over Bluetooth specially with the AAC codec. SBC sound "okay" but still under performing comparing to OOS.
I have a similar issue. I disable Dolby in favour of v4a, but the issue persists. It's like the connection with the BT device is unstable - like the devices are too far apart even though they are inches away from each other.
To be fair, when they are next to each other it works fine - it also works fine in my car. But if I move my phone more than 4 inches away from the soundbar on my desk I get this issue.