The flaw could be the tongue on the right boot. It might not stay centered and over time might ride to the left. This happened with my first quality Daltons. The options were: deal with it or have the cobbler stitch the tongue in place. I decided to deal with it and adjust through the day because the boot can be difficult to get into with the tongue stitched in place.
I've noticed that as well, yet, as you put it on, the tongue becomes perfectly centered.