Do the straight bits ever curl? Like, say, when it's really humid? Some people just have a really irregular curl pattern. I know I do. I just live with it -- I've gotten used to how my hair looks, and I don't expect symmetry. I have some much straighter pieces right on the sides, very visible. But it is more uniform when the humidity is high.
The only other thing I could think to try would be clipping the outer layers while drying, somehow, just in case their weight lying on top of the underlayers is making them straighter. But this might not be the issue.
Wurly and proud!
Modified CG since 2008.