2015 Prius 3 iOS + Bluetooth woes

Howdy,

Before I start, let me say that I've googled the crap out of this, and searched the Prius Chat forums, and even taken my Prius to a dealer before I decided to post this, so we can shelve the requisite "did you search for it...?" questions.

So, here's my issue: I've got an iPhone 7 Plus running iOS 10 and I drive a 2015 Prius 3 with the standard nav head unit, and I have constant but impossible to replicate on demand issues with bluetooth streaming from my phone. Specifically, anytime I try to stream music via bluetooth, it eventually (within 2-25 minutes) starts to "stutter" the music, like a scratched up CD would. Occasionally, the stuttering gets so bad that the music just stops playing and bluetooth stops working entirely. At that point, to get bluetooth to stream again, I have to turn off the car and reboot the phone.

Here's the weird thing: using bluetooth for phone calls works perfectly fine - no audio or connection issues what so ever. Siri also works fine through BT. It's just streaming any media (Music, Spotify, Pandora, Audible, Podcasts, etc) that causes this issue.

I've been plugging into the USB port, and that works fine, but I'd really prefer to use bluetooth. It's a convenience factor, but also the USB port in the Prius isn't a 2.4A port, so it also doesn't charge the phone as fast as my Anker 2.4A charger that's plugged into my cigarette lighter.

I've tried the following:

1. Paired and unpaired my phone to the car (both on the phone and the car) multiple times.
2. I've completely wiped and restored my iPhone 7 Plus (done both an iCloud restoration AND setup the phone as a new device).
3. I've reset the "Network Settings" several times (incredibly annoying since you lose saved wifi pairings too...)
4. I've gone through troubleshooting with the folks @ Apple over the phone - even with a senior agent who deals only with bluetooth and wifi issues. Nada.
5. I've taken the car to my dealer - twice - explained the problem, sat in the garage with them (and of course it didn't want to replicate at all over that 10 minute period of time). They couldn't find anything wrong and refused to replace the head unit on principal (despite the fact that I've got the maximum extended warranty and even offered to pay out of pocket for the labor).
6. I've paired a friends iPhone 7 to my Prius and was able to get the problem to replicate after a 12 minute drive.
7. (EDIT) Forgot to mention, I also installed the August 2016 Entune radio update last month hoping that it would fix the issue, and it didn't change the issue at all.

I'm at wits end with this problem. The dealer refuses to acknowledge it's a problem with the car or the head unit, despite the fact that I only have this issue in my Prius, and not my wife's car - nor with any other bluetooth accessory or stereo.

Does anyone have any ideas or suggestions on what I can do here?

Thanks in advance.