Corridor samples with empty shapes

[jameshitt]

I have a corridor built with a custom subassembly that in a few instances doesn't show shapes that are supposed to be there:

It isn't a targeting problem; there is plenty of surface, and all the target points and links are being made. But I keep getting these random samples that are missing shapes. Has anyone run into this?

[SoaresASBCAD]

https://forums.autodesk.com/t5/civil-3d-forum/corridor-shape-problem/td-p/6821766

[jameshitt]

@SoaresASBCAD  No, that post is a different problem. My corridor is targeting the target surface correctly, and it is building the points and links out correctly. My problem is that on a few corridor samples, some of the shapes are missing for no reason I can figure out. See below: