Brake Master Cylinder problems of the 2017 Toyota 4Runner

I pulled up to a stop light and applied the brakes. I stopped but while I was sitting with the brakes applied, my 4runner started rolling forward. I had to push the brake peddle to the floor to a point I could barely reach to get it to stop again. I took it to the dealership and they agreed the brakes were not acting right. They could see on the computer that something was wrong as well. They said I would need a new master cylinder on the 4runner. The vehicle is only 2 1/2 months old with 2500 miles. When I picked up the vehicle, they said they talked with Toyota and it was only the 2nd case of this happening in the us. The morning it happened it was around 30 to 35 f outside. When the dealership tested it they said they applied the brakes to stop and it slowly started moving forward after a few seconds like had happened at the stop light. They replaced the master cylinder and when I picked it up everything seemed to be working ok.