Picked the car up this afternoon. They replaced the rear junction box, but the Service Manager does not believe that is the problem that I was experiencing. After much conversation, and research I believe the auto stop/start was engaging early. When it happened, I brought the car to a stop, and at this point I thought the car was dead. I then put it in Park and the car then turned completely off. I then pushed the Ignition switch to turn it back on. Consequently, I am relieved that no catastrophic failure was found and that I now have a plan if it happens again. So, not a complete imbecile in that I did not turn the car off, but I did set the car up to turn itself off.

If when it turns off, instead of selecting park, just apply the park brake and take your foot off the brake and if it restarts that'd confirm it was the stop/start working.

Agreed. When it originally happened things were moving fast and I was caught off guard. The last couple of weeks have given me an opportunity to analyze and hopefully develop a workable strategy going forward. We shall see...............

Disconnect the stop/start and see if that cures the problem.

Clearly, if the start/stop system is suspected as the culprit, the the first thing to do is to eliminate that possibility to check -or eliminate it entirely by permanently disabling it unless the car is regularly used in stop and go traffic (in which case the stop/start system is even MORE annoying!).

Service Manager said they could not disconnect stop/start. And I'm uncomfortable doing it since I don't know what else will be impacted. Thanks for the suggestion.

Just pull the plug. No ill effects.
Thanks to Tel for how to...
https://i.postimg.cc/NFBmF2BL/730634...8-EBB0-FA1.jpg

Thanks for the help.

Slowing down to stop sign Car died AGAIN. 27 hours after picking it up from dealer. In Sport mode, Dynamic with Start/Stop off. Car shut down, I saw the Red battery icon on the dash when shutting down. Car went into Park on its' own when shutting down. Bringing to dealer in am. Car has less than 500 miles on it. 300 while dealer has had it.

My conversation with the Service Manager was very direct. Not his fault, very nice guy, but I partially lost it. Eventually recovered.

Does know the code for the trunk/boot tub liner clips? My felt trunk liner piece is detached near the opening of the trunk (convertible) on the side closer to front of car. There are remnants of some adhesive but bending the liner alone wasn't sufficient to get it to stay in place.
The dealer initially said they could try replacing it with new clips, but later said the tub is distorted from previous removal and I would have to replace the entire felt tub.

At his point I don't think it is part of the Start/Stop function. This is getting old. Could a faulty alternator, or wiring to the alternator cause this? After re-starting the car and driving away, the red battery icon flashed momentarily in the dash. (Fraction of a second.) No loss of power.

The dealer cannot disconnect the start/stop system for obvious reasons, but you can. It is child's play....and nothing else, nothing is affected by disabling the stop/start system. This 5 minute job (if you are slow) will tell you once and for all if this system is the culprit.

But if the OP had disabled the stop/start and the car actually went into parked mode by itself when it stopped would surely indicate something other than the stop/start being at fault? Stop/start never goes into park when you brake to a halt.

Hard to believe it went into park. Maybe he had his thumb on the button.

On at least 2 of the 5 times this has happened, both hands on the steering wheel. I was doubting myself after the Service Manager could not replicate after driving it for approximately 300 miles in 9 days. Last night I stopped doubting myself, it is not driver error.

Hopefully there was a code registered. Have them check for paint where the battery ground wire is attached. If the ground doesn't have a connection to bare metal it has caused gremlin type problems for others in the past.

OP, has your dealer considered looking for a faulty driver's presence sensor in the driver's seat?

Here is why:
I think it's an important thing that the car shifts into park automatically.
And another important message is that it only happens at low speed.

There are many sensors that will automatically shift the car into park. Modern car safety features. Safety features won't shut down engine when the car is driving fast.

For example, when you try to drive with door open, car will try to stop you. A bad sensor at the door latch would cause some issue. That's probably not your issue, because you would otherwise get message of door open.

Maybe it's a bad driver's seat sensor? If the sensor wrongly thinks the driver is not present, the car may shut off engine, put into park and shut off entirely.
This is to protect for the case where driver exits the car forgetting the car is in drive and the engine is on.
I would put my money on this one.

Just my thought. I am no expert at fixing cars...

I appreciate the advice and will discuss with the Service manager. The car now will shut down, but remain in Drive which is even crazier. The Shop Foreman thinks the it is significant that the Red Battery Icon lights up on all occasions. He thinks it is a problematic wire somewhere in the system. He told me he checked all of the obvious areas yesterday morning. Car died three times yesterday. On one occasion I was able to take pics of the dash and shifter. Other two times in heavy traffic so no time, Thanks.

And you still do not want to disconnect the start/stop system to test? It will take less than 5 minutes and will have no effect whatever on any other function of the car. If the symptom disappears with the start/stop system disabled, then you have identified and isolated the problem. If, on the other hand, the problem persists with this ultra-simple test being made, you will have eliminated the stop/start system as the culprit. Either way you will have gained a better understanding of the issue (and so will the rest of us). It will cost you nothing more than a few minutes of your time.
And it is true that in many instances the dealers know LESS than the collective voices on this forum. Please disconnect the start/stop system and report the result.