The front head restraints on my 2018 A5 Cabriolet are operated by moving the backrest control up and down but they did not appear to work at all when I took delivery of the car a few weeks ago and I asked Stratford Audi, who supplied the car, to check and correct this apparent fault. This was done and the car was returned to me. Sure enough, the driver side head restraint was now adjustable but not the passenger side. So, I contacted the dealership again and the car was duly collected for the work to be completed. However, I received a call from them to say that the passenger head restraint was working BUT, did I know that these head restraints do not function if the seat is set at its highest setting? I had seen no reference to this in the manual but, nevertheless, the service manager said the function is disabled because it would obstruct the roof opening and closing and that a radar sensor detects this and switches off the adjustment. Now, I have come across several instances where the power head restraints have not worked. In one case, the 'fault' was corrected by the dealer on three occasions but, by the time car was back home, the 'fault' had returned. It is worth checking, if this is your experience, that the seats are not set at their highest setting before contacting the garage. I guess there's always something new to learn.