Solid object loses back and front faces

Rhino
1

i have a complicated line drawing.
I can curve bool or planarsrf to get a supposedly legal surface but when i extrude it loses the front and back surfaces but still says it’s a solid.

i suspect it’s the line geometry that is the problem but it seems to be ok.

i can DM the file

Thanks in advance

image
image870×948 81.2 KB

2

Hello - I would check for self-intersections the border curves - please post the file or send to tech@mcneel.com with a link back here in your comments.

-Pascal