Not sure if this is a Bug or not, But i have found that if your using a IOS application that has an option to have access to the microphone streaming music via Bluetooth will not stream, all you will get is dead air. If you turn off the access to the microphone for the specific IOS application then streaming via Bluetooth will stream correctly. I was using Amazon Music. I have tried this on several IOS device in the house and several Volumio Installs running on Raspberry PI3’s