Hi Burr, I'm not 100% sure what is happening there, the edges do not seem to sag away from one another, but also the edges between different pieces are not exactly aligned with one another, some of them have different endpoints although not very far away.

I took a close look into one problem area and it looks like there is some crossing overlap between some of the edge curves, that may be the problem.

Like for here I marked the end of this edge with a point:



Now if I go select the edge right next to it you can see this:




I'm not entirely sure if that is the problem though.

- Michael