[SOLVED] Self created spline - Wrong terrain cutting

Well, one problem rarely comes alone...

This time, it's my own pavement spline, which causes the problem:

Only the curbstone:

And with the pavement:

It creates huge holes everywhere, an it gets worse, the more is added. Polygons doesn't cover these holes either.

I also tried it in different maps, all the same. And importing it as a standard spline, the same happens.

It looks like this in Blender:

After importing it to the content tool, just to test it out, I immediately clicked the big Save and Pack button. So no settings changed in CT at all.

What's causing such a simple spline to create such huge holes? What can I do?

It works now, thank you so much Marcel!

There was an old extrude I didn't notice, so pressing Remove Doubles did it.

Plus, now from the underside in the Content Tool, it is invisible. Before it were visible from both sides.

Left one is the new, right one is the old:

-Thor