If the behavior you're describing occurs, then it is most definitely a bug.
Consider checking to make sure that if it is indeed plotted, you can expect the linework to show up. By this I mean look at the View Attributes to make sure the attributes are the same between the two cross section models, and that Level Display is the same between them.
Another practical troubleshooting question that just came to mind: How long is the range over which you expect the 3d elements to show up in either of the two sets of cross sections? It is conceivable (though unlikely, I expect) that the linework doesn't show up in the one set of cross sections because that linework is somehow interrupted right at the cross sections.
I'll be surprised if Bentley's people will see this and not ask for your file, so you might want to save the time and upload your relevant files in a package. Instructions are provided with the advanced reply editor. Meanwhile, I would not be surprised if they do not look at it within the week before it decays from their system (as they've done to some of my uploads), so you might want to save your work in a ZIP file so that even if you have a workaround established by then, you can re-upload it when they're ready.
Consider checking to make sure that if it is indeed plotted, you can expect the linework to show up. By this I mean look at the View Attributes to make sure the attributes are the same between the two cross section models, and that Level Display is the same between them.
Another practical troubleshooting question that just came to mind: How long is the range over which you expect the 3d elements to show up in either of the two sets of cross sections? It is conceivable (though unlikely, I expect) that the linework doesn't show up in the one set of cross sections because that linework is somehow interrupted right at the cross sections.
I'll be surprised if Bentley's people will see this and not ask for your file, so you might want to save the time and upload your relevant files in a package. Instructions are provided with the advanced reply editor. Meanwhile, I would not be surprised if they do not look at it within the week before it decays from their system (as they've done to some of my uploads), so you might want to save your work in a ZIP file so that even if you have a workaround established by then, you can re-upload it when they're ready.