Hi Bdaniel, thanks for posting the file.

So the problem is that in one area the 2 conic segment pieces are not touching end-to-end, instead they are overlapping each other, crossing over each other a little bit instead of touching end-to-end.

The problem is in this area here:




Here I've moved one segment a bit to the side so that you can see the kind of overlap that is happening there:




But also you've got some other problems with the bottom part not being all planar as well, it looks like some of the vertical curves do not have their ends touching all the way to the bottom plane, some are floating a bit higher above the plane than others, you'll want to tune that up by turning on their control points and then going to a side view and then using either the Transform > Align tool to line up their end points to a common bottom line, or use the edit frame with "flat snap" to make them all in a single line, as shown here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3378.4

You can see some of the non-planar-ness if you zoom into this region here in a side view:






So what I'd recommend is to delete the conic pieces and first focus in on getting the vertical curves to have a nice common flat endpoint - do that by selecting them and then using Edit > Show pts, then go to a side view and drag the corner of the edit frame down until you see that "flat" snap activate, that's when you'll know they're all in a line. And then it would not hurt to drag the bottom ones to be right on the z=0 plane as well. Then also make sure the top points are all in a flat line as well. Once you have gotten those curves to be all properly aligned then do the conic pieces.

Let me know if you need more help on how to fix the end points of those vertical curved pieces, you will not be able to put planar end caps on their ends unless they are all lined up on the same line basically.

- Michael