Inverted paths (paths inside obstacles, looks like its playing 'dont touch the floor')

This question has been retracted.

The problem was that the pathfinder was plotting paths ontop and inside of walls, and generally everywhere it wanted to.
(It was preferring either a straight line trough terrain, or plotting a long winding path ontop of the walls)

The solution was to add a real floor made out of vertices, and not have it walk ontop of a plane.