My and my wife's Fitbit have constant Bluetooth issues to our phones. This is completely and utterly annoying.
Driver related? Not sure.
Well, is the bluetooth as good when your wife is driving the Rav4?
Check out the PCB guidelines for the popular NRF51822 Bluetooth tranceiver:
https://devzone.nordicsemi.com/blogs/655/general-pcb-design-...
It barely scratches the surface, and in reality there will always be some trial and error as other nearby circuit elements can cause unpredictable interference or feedback. But it's a lot more finnicky than laying out an Arduino board.