Try putting your phone in a few different places to see if the instability is dependent on the phone's location. I've had problems with maintaining a stable Bluetooth connection for audio ever since I got the "infotainment upgrade" (more modern infotainment computer driving the main screen) in my 2015 Model S. For me the connection is useless if the phone is on the center console and works pretty well when it's in my pocket or jammed under my legs in the driver's seat. I've tested less on the passenger side, but on a recent road trip it worked poorly with the phone in my hands and well with it stuck in the passenger-side door-handle pocket.
It works fine with my wife's Samsung, but Samsung tries to make its phones work with other compaies' products and I'm stuck with an iPhone.