What does the beeping (Red Brake Light) mean?

it happened to my car also 2001 ml 320. First I heard noice and yellow circular light comes on and then slowly my car move when esp/bas came on. I bring to the dealer and they fix brake pedal switch because it is recall no charge, then next day again, the same situation came and the esp/bas came out. I bring back dto the dealer that the swith is defective, they told me it is not and i had to pay $125 to do diagnostic code. any help how to fix it. Very scary when you are dring in the expressway. I had a new front brake pads and rotors.