2015 Audi A6 Steering problems

While driving at night there was a flash flood on a known flood road. After proceeding through what was maybe 6"-12" of water, vehicle's amber steering defective warning light appeared with the notification stating that the vehicle was safe to drive. The next day while driving, the amber steering defective light turned red with a notification stating not to drive the vehicle. Upon this happening, the vehicle lost all power steering, tpms fault, stabilization fault, and acc braking guard fault appeared. Thankfully,...

Exhibits an alarming tendency to weave from side to side without a steering input. This occurs without a change in steering wheel position, vehicle speed, or change in road surface or prevailing wind direction. It is more pronounced at highway speeds and when wheel is centered at 12 o'clock but does occur at all speeds and steering vectors. Audi dealership notes the problem and blames the new electric steering system but states it is a "characteristic" of the system and is not a defect. I disagree and feel any direction change in a vehicle without a driver input or a explainable external factor constitutes a potential safety issue.