I think your post may have fixed my issue! I have been having the "phantom controller/low battery critical error" over the last couple of weeks. Have been working with Oculus Support to try and fix it but none of their suggestions were working. I found your thread yesterday and it made me pay attention to the sound when my error occurred and they seemed like they might be correlated. So I decided to plug in a set of earbuds and give it a try, low and behold I am able to play without a hitch! I have been able to get my headset volume up to 80% without earbuds, at 90% the error returns. I will be updating my support ticket with this info hopefully, they can give it a quick fix for all of us.