Bluetooth audio continues to play when answering call

Since updating to iOS 11 if I am playing audio over the Bluetooth connection in my car and receive a phone call, the audio continues playing in the background at the same time as the phone call.

The caller cannot hear the background audio - only I can in the car. This also happened to a friend of mine when I called him - he was talking to me and his music kept playing in the background during our call (I could not hear it, but he mentioned it). Coincidently, we both have Ford vehicles with a Microsoft Sync bluetooth audio system.