How come I have a persistent patch of straight hair?

I've been enjoying my curls for a few years now. It's all healthy and as frizz free as I can ever hope for it to be. The texture is pretty uniform and I'm happy with it...except that I have a patch of hair on one side that insists on remaining straight. In the last i presumed it was due to heat damage but as times gone on its apparent that this isn't the reason. Even after a deep condition the texture is a limp wave, of that, and a few hours later is straight. Any ideas on what might be the cause or solution? I'm thinking I'll have to put rollers in that section but the texture isn't right...

2 Answers

It actually may still be heat damage, as heat damage can't be reversed. The only solution to getting it naturally curled again would be to do the big chop.
It can't be that though, because the reat has grown out, and I've not been hear treating it for ages and this patch is straight from the roots