What causes this?

These words he speaks are true.

I'd say ask me how I know but I'm not reliving that.
If you're old enough, you may remember Ford had that exact problem all through the 70s. Some cars would jump into reverse from park, if the driver got out and left the vehicle running. I believe a few people were hurt and maybe even a couple killed because of that. The vehicles would usually end up doing circles in reverse before hitting something and getting stopped.

I don't know who Ford blew off to get out of a real recall, but the only "recall" they had to do was to send out stickers to the owners of all the affected vehicles (There were a LOT. 23 million at the time. The largest "recall" of the time) and place sticker on the dash saying to always set the parking brake, etc, etc. It was pretty stupid. We had a 76 Maverick at the time that was Mama's and I remember that sticker well. Here's an article that tells all about it.

https://www.theautopian.com/how-for...icker-to-dodge-the-biggest-recall-in-history/