Stencil 2D Linestring/Chain to 3D Mesh drops to line elements?

Hi all,

I'm trying to stencil some very long linestrings/chains onto a 3d mesh and am finding the results are many individual lines. They are being draped successfully, but is there any reason why the linestrings/chains are being dropped to lines? There are so many that is not very practical.

I'm using MicroStation CE U12/OpenRoads Designer U7, but see the same behaviour in v8i.

Regards,

Mark