Fill SubD hole

I don’t know why. When I choose the hole edge of the SubD, it’s not closed as normal. But when I just choose one segment of the edge, it’s closed perfect. I think maybe it’s because that the fill command is for the inside hole in SubD, while it occours to the edge, it can’t tell the direction, but most of them are correctly closed. So I just wonder why. And the principle of the fill SubD hole command.

I’m new for the rhino & GH, thank you for your help. Vielen Dank im Voraus!

Hello - please post 3dm file with an example of the case you are asking about…

rain pipe casting for help.3dm (1.1 MB)

one side is okay, please help to check the other open side! Thank you very very much!

Hello - I see that, and I do not see why - I’ll put it on the pile for the developers to have a look.
RH-64424 Fill - ugly at one end


Thank you very much!