IOS 10.3 audio phone call not routed to bluetooth in BMW car

[Spiney13]

With iOS 10.3 a bluetooth issue is present where the audio of phone calls is not routed to the bluetooth device.
In my case this is a BMW. When setting up a call from the bluetooth device iPhone shows that audio is routed to the iPhone itself in stead of bluetooth device. Microphone and speaker of iPhone are used. Audio of phone calls is routed to bluetooth device only if manually switched from iPhone to bluetooth device.
Issue: Music audio is routed correctly but audio of phone calls has to be switched always manually to the bluetooth device in a BMW. Problem was not present with IOS 10.2 and 10.2.1 for myself.

 

[BBDDVV]

Update: iOS11 solved this for me...

for me it's hit and miss with outgoing calls. Incoming calls are always fine.
The issue I'm seeing is that there is a large delay (up to 5s) between pushing the button on the steering wheel to accept an incoming call, and the call actually be answered...