2005 Audi A6 quattro 3.2 - Was driving this morning about 3 blocks from my house after our first snow. I let the car warm up for about 15 minutes before driving. Stop sign one no problem, sign two no problem, sign three three beeps then abs light and flashing brake light. Messages says brake failure and take the car in right away. I turn off the car and turn it back on and get the same issues. Any thoughts?