Openroads underground utilities on cross sections

Hello,

This may be more of a Microstation question but I'm using the process with Openroads.  I am using the "Solid by Extrusion Along" to create 3d existing underground utilities.  I'll first use the Horizontal "Complex by Elements", then create an offset vertical from the existing terrain.  That results in a 3D Linear element.  After applying a solid to the linear element, I get a nice pipe circle on the cross sections.

The problem is...sometimes the "Solid by Extrusion Along" works and sometimes "Unable to generate geometry".  I can't seem to get a feel for what the criteria is for it to work.  Sometimes a complex horizontal (lot of PI's) and complex vertical will extrude.  Is there a max number of horz.. or vert. PI's?  Don't use curves?  Or is there bettter way to accomplish this task? 

Microstation 08.11.309.608

Geopak 08.11.09.722

Thanks

Rick