It was a moment of stupidity!
On the top of the wing when I prepared the spar cap to be drilled I laid a referrence line out on the top skin 2 inches from the center of the spar cap.
That way when I put the nose skin on I could easily recreate my drill line.
But on the bottom I forgot to draw the reference line, and out of a desire to save the hour it would have taken to remove the nose sking and draw the line, I decided I would mark the flange center on the ends of the wing where I could still see it and use a straight board to layout my rivet line.
This might have worked if the board was perfectly straight, if the spar was perfectly straight and I had absolute control of the sharpy.
In other words sometimes you can get away with being dumb, but not this time.
In order to save an hour I lost 3 weeks worth of progress.