I'm having different problems with Android and phone book transfer, after removing one of the multiple accounts which support contacts... Not fixed yet but you may be able to force a change of behaviour by:

Settings - Bluetooth - hit the settings gear wheel icon for the relevant "Paired device" and uncheck "Contact sharing". Try again. If no success, scrub the pairing and repeat. To scrub the pairing, put the car into pairing mode and hold down the button until you get the audio tone and message on monitor (if present).

In theory this should change the connection protocol (Android supports multiple protocols) and it might help you restore the audio connection to normal behaviour.

[For Linux users who are curious about supported protocols in BT devices you can use from command line ' hcitool scan ' and' sdptool browse <bt address> ' to see what each end supports. Note that contacts transfer in BMW ULF supports non-standard workarounds on some devices so even with contact sharing seemingly not supported it can happen - and vice versa...!]