hi,
try and check if the crosscurves producing the breps/polysurfaces are going in the same direction. It seems like one of your surfaces is reversed in grasshopper. very easy check would be to use the ‘reverse surface’ node and check which one of the volumes is inverted.
Basically if you make a boolean union (addition) between a positive and a negative volume, you’ll end up with a substraction. I’m pretty sure that’s what happens with your model.
I hope this helps a bit. If you need further help, it would be good to attach the file.
EDIT:
In the meanwhile you can check out this simple c# script flip the direction outward if necessary. You should put it right after the sweep nodes:
xFlip.gh (2.3 KB)
As said, I don’t have your example and don’t know if this is going to work, but I’m pretty positive.
Ben