I would love to hear that this is just something stupid I’m doing :)
I’m sure it isn’t, but the only area in which the framework can really affect bluetooth usage is during initialization since it is a standard that is implemented in the hardware layer by Apple, and initialization is apparently going fine to judge from the OpenEarsLogging output, so I don’t have a lot of suggestions – there’s no possibility of testing Bluetooth against all possible devices and it’s working with all the devices it’s been tested with.
Are you absolutely positive that there’s nothing special about the headset in this interaction (low on battery, far away, muted, being overridden by a different, nearby bluetooth device that you aren’t interacting with, something else similar)? When the sample app isn’t working, what does the decibel label read, is it moving or fixed? Can you try a different bluetooth device with the sample app?