Just be happy it isn't a concave movement. Is the OSB actually thicker in the middle now? Are you sure the back did not warp and take the OSB with it? To me this is more likely, the back piece shrinking and cupping and the OSB just followed...
Did you throw the straight edge across the back ??
I can just see it now...
Q: "How is the action on that Tele?"
A: "Depends on humidity..."
Q: why do you only play slide when it's raining ??
A: ppfffftt....
Have you considered a dual micro tilt setup??
