[rosethornil]

That happened to me a couple of times, i would say at least 5 times while backing up from a parking spot or my driveway but not the flashing brake sign. It alert me that someone is behind or a car is behind me when there isn't. I would wait a couple of seconds for it to stop. Usually happens if its misty outside or if it rained or is raining. My guess is that it was beeping and you kept backing up and that is why the flashing brake came on? What is the sensitivity level at?

My shiny new 2018 XLE also did this, alerting me that there was a pedestrian behind me, when there was nothing. I was backing out of my spacious garage, into a big expanse of concrete.

Freaked me out a bit because I thought - for a second - it might be a nefarious type!