Brake Light On problems of the 2016 Ford Fusion Hybrid

Our brake light came on spontaneously for several seconds while car sat idle with parking brake off (my spouse was in the car and saw this happen). We turned the parking brake on and off, but the light remained on. It went off after about minute by itself. We took the car into the dealer service center to check that issue and do an oil change. They did a "vehicle check-up" (we have the paperwork) and said there was no problem found. Three days later the brakes failed. I was driving on a surface street, crossing straight through an intersection with a green light at around 10mph (I am guessing), and went to slow the car because traffic had slowed. The brake pedal went soft to the floor, yet the brakes barely had any force (I am guessing 10% stopping power). The brake light came on and a beep sounded. I was able to navigate safely to the side of the road and slow the car to a stop. We towed it to the dealer service center. They, again, said there was no problem. They indicated that it could have been the collision mitigation system warning I heard, despite the fact I have had the car for three years. . . I know the difference. Furthermore, my spouse saw the brake light come on earlier. Most important is the fact that the brakes failed. We also called Ford headquarters and informed them of the issue. We were told they investigated this at the service center, and found no problem.