so these unintended accelerations are missing one point - physics. The brake is a physical metal bar that connects to a physical tube filled with hydraulic fluid that connects to a physical caliper / pad / rotor. While there is electronic assist, the brakes will work without the electronic assist, and the way that the electronic assist is implemented it is physically impossible for it to cause you to not be able to brake. What this means is that NO MATTER WHAT, if you hit the brakes, the car will stop. You are literally applying a clamp to the wheels directly and without the computer being able to intervene.
On top of this, even at maximum torque of both motors, the brakes are able to rapidly and quickly stop the car. So lets say even if the car accelerated on its own, for the sake of argument. Your foot on the brake would 100% overpower the motor immediately. brakes are EXTREMELY powerful
There is literally no other way around this.
So the second you felt the car accelerating not the way you wanted it to, you hit the brakes and stop the car. period. if it is legitimately accelerating on its own, turn it off while you have the brake down and call for a tow.
In no scenario does the car "drive itself into a tree/fence". It means you didn't hit the brake or if you did, you didn't hold the brake down.
Regarding the bad weather message from autopilot - I get this all day long here in new england every time it thinks about raining. unrelated.