Rear wheel backspacing

Since at Ford quality is job 1, you can expect some variance. But that sounds a little excessive. I would swap the tires from one side to the other, just to make sure the buck-toothed side doesn't move with the wheels (possibly a wheel issue?).

But before you do that, measure the distance from the tire face to the inner edge of the fender lip (at the top center point). Do that by setting a straight edge on the tire and measuring from the straight edge. A level works well for this. That way you can make sure it's not just a perception, angle of perspective thing.

good to hear.