Same issue here a few weeks after having some work done.
Had only driven about 3 short drives, and then had power steering fault pop up and go away a few times. Then one day driving straight down the highway had power steering fault come on followed by rear wheel steering fault a few miles later. No change after disconnecting battery for a week in the garage, and awful driving at slow speeds without power assist.

Dropped off for a day at dealership and they discovered a loose ground connection on a bolt somewhere in the rear as a result of the recent work performed. Tightened up and all good again.

 

why are these cars SO sensitive to voltage issues that manifest as faults in systems like RWS, PADM, PASM etc ...