I've been selling the Zeiss ZM lenses in Canada longer than anyone else.
I've sold 100's of the lenses.
I have yet to a single unit returned because of the wobble.
People seem very happy with them and I use them myself and have had no issues.
The Leica gear is great as well. Wonderful look to the images and great build quality.
I think if they were the same price I might choose the Leica gear, but since a new lens is 5X the price I find it hard to justify for myself.
Of course your mileage may vary.