Like others have said, if someone is making a turn from your lane and it doesn't think you're going slow enough it will trigger a BRAKE! message. Unfortunately I've had a few instances of people suddenly moving into my lane that would have resulted in an accident if I hadn't slammed on the...
I listened to the latest clip you uploaded and it sounds very close to what I experienced. Double check these two connectors under the passenger seat are in place. In my case, it was the clip behind the one in front. Hope this helps.
I fought with a similar rattle coming from the passenger seat over rougher roads for a few months before I found the problem. Under the seat should be a couple of white clips that attach to metal rods. Although they're toward the back of the seat, you can only see/reach them from the front...