Help/Opinions Needed - 2015 QX60 Rolled Backwards in Driveway

Hello fellow QX60 owners. I am new to the forum. In fact, other than radiator fan bearings, we've never had any issues with our 2015 so I never thought to seek out a forum. However, we had a recent incident that made me start doing some research and I thought a forum of other QX60 owners would be a great place to share the situation and ask for help and opinions.

What happened: My wife, who drives the car daily, went to pick up our son from a friend's house and pick up dinner for the family on the way home, parked in the driveway and, as she and our son were getting out of the car, it began rolling backwards down the driveway and ultimately stopped after hitting the curb on the other side of the street.

I've uploaded the video from my Nest Doorbell camera: . Pictures are below.

So, first things first, nobody was hurt and I am extremely grateful for that.

Another thing right off the bat, I have no idea what happened and I'm not sure I have any way of ever knowing what actually happened. Upon first viewing, the most obvious assumption is that my wife somehow didn't put the vehicle in park when she pulled into the driveway. I get it and am not going to argue with anyone who is convinced that is the reason why it rolled backward. The only thing she can remember is that she immediately tried to press the brake and the brake didn't work. She doesn't remember trying to move the shifter at all and the short amount of time that this occurred in suggests that she only had time to try to press the brake. If you watch and listen to the video, she has to start the car in order to move it back into the driveway and there is no engine sound at the beginning of the video so the engine appears to have been off when this happened.

What I am after is opinions on whether or not it's possible that the issues that are behind the CVT warranty extension could be at the root of this? That would assume that the vehicle was in park when it happened, I know. Which is why I'm taking the time to ask if it is possible. If it's possible then this is a pretty big deal. If it isn't then I've only wasted my time in writing this and you fine folks' time in reading and responding. It is worth asking.

Let me explain why I'm even entertaining this as a possibility. My wife, if you ever got to meet her - rather ride with her in her QX60 - is that she always puts the car in park and sets the parking brake. Every time without even thinking about it. It's just second nature to her. That doesn't mean that she didn't get distracted, but I'm telling you that if you knew her, you'd realize how unlikely that would be. Again, not impossible, just not very probable.

Another reason why I'm entertaining the CVT being the root issue is the audio from the video. After the noise of the door scraping against my truck, it sounds like there is other noise - clicking/ticking/whatever - that sounds almost like the transmission didn't lock into position when it parked and it was making that noise as it was rolling backward.

After that last sentence, I'm sure it's apparent that I'm no mechanic and I don't really understand the actual mechanics of how transmissions work. Yet another reason why I need to ask for help and guidance.

Honestly, I am open to any questions, comments, suggestions, opinions, or wisecracks. Just please keep them on topic. Ha!

Jeremy