Did you get to the bottom of this?
My van has gone light on the steering and there Is a slight vibration feeding back through the steering.
It also some time feels like it moves right like if you have hit ice,but no traction control light on at this time?
My mate has had it on the ramp in his garage and can not find anything that is worn loose or damaged,the only thing we can put it down to is the tyres they are cross climate agilis that have been on for about a year and a half.
Will have to swap over my wheels from my T5 to see if it makes a difference.