Original firmware was recycling power every 20 mins on zoom calls. One of the later software updates fixed the issue (thank you!).
Now, I am on v2.1.143 and when connected to my iPhone 13 iOS 15.2.1, they play no sound. macOS 12.2 device plays alright.
I made sure to press volume up many times. Pause and other touch controls work, tried to re-pair them to the phone to no avail.