I got a Oculus Rift S a couple of days ago. It worked prefecly for me and I played a couple of hours Half life: Alyx. Out of sudden the sound became crackling (like scratches/ dust on old audio records) in the middle of a game sequence. I finished the game and checked possible root causes for this issue. I didn't changed anything witin my setup.
I fear that it is an connection issue within the internal audio speakers and not an driver/ software issue!
I restored a backup of my Windows 10 installation and re-installed the Oculus Software and Oculus Rift S device. Crackles are still there. I am pretty sure that the issue is due to bad contacts within the internal speakers. I removed the plug of the internal headset and plugged it in again. Still Crackels!