One problem related to speed control cable has been reported for the 2018 Audi S4. The most recently reported issues are listed below.
When driving in manual mode and transition from on the throttle to off-throttle, there is a 1-2 second delay before the engine stops accelerating and transitions to deceleration. Especially in first gear, this means that the vehicle continues to accelerate for that period of time. I drove another model of Audi with the same engine/transmission (2018 s5) and it exhibits the same behavior. Since the car does not have a physical throttle cable, this would seem to be caused by the throttle not closing as commanded by the ecu or there being a delay in the throttle being commanded to close. This has not caused a collision but easily could.