Yeah, try to reproduce band 1 in band 9, and set band 1 to zero..That'd be a really obscure bug if that is indeed the issue.

Oh wow, now this is interesting.

When I reproduce the details of band 1 in band 9, then I set the gain parameter on band 1 to zero, the distortion gets significantly worse. But at worst, I should get the exact same sound out of either configuration, shouldn't I?

Something is fishy!