I have the same issues at low speed on a 2010 CTT. However in the wet and slippery conditions it feels like it’s dragging its back wheels. At high speed I have had one rear wheel lock up on the rear and throw the car sideways while joining a motorway. The problem got progressively worse locking up on roundabouts at slow speeds on a trip to the mountains. Obviously made us quite nervous driving up mountain roads etc. I have now pulled the PTV fuse and all it smooth again. My question is would an oil change make a difference, rebuild kit or just a stepper motor rebuild? No fault coded prior to pulling the fuse.