I tried that as well. If I leave my iPhone connected and switch it to silent so that it doesn't make the charging sounds it will eventually give up and work very very weird. It is probably a software problem with the car.
I have 9.1 and it's worked fantastic. Bluetooth and USB, never once had the issue you are showing. My first suggestion would have been the cable as well, but if it's working on your wife's phone, i'm honestly not sure. You can get on the public beta for 9.2. I'm using it on a phone and it's also just fine.