I am seeing the same thing on my Samsung s7 since the last update. I use my google maps A LOT and before the update, I paired my phone with the car and put source for the car on FM, AM, USB, or AUX, and listen to those sources and the voice navigation came from the phone. Incoming calls came from the handsfree through the car. Since the update, when I am connected to the car's bluetooth the voice navigation will only go through the bluetooth and if you are not set for bluetooth as the source on the car you can't hear anything. I am still waiting for a fix to this.