I have a Seat Ibiza with a Garmin navigation system: https://seat.garmin.com/seat/site/productOverview
Pairing works fine and starting a call works fine, but only in roughly 1 out of 10 tries the sound is working. Meaning the call is made, but caller and callee can neither hear each other.
If the voice is working, the phone hangs after the call ends and has to be rebooted, before I can make a new call via BT.
Music streaming via bluetooth is always working fine.