Looks like the curved wall is intersecting on itself, maybe that is causing the problem.
How up close are you going to be looking at these?
If you look at the example below, I've made the fences which are supposed to be 30 mm round wrought-iron simply by extruding a profiled wall 30 mm. They're square, but the image I want to convey comes across no problem.
http://home.quicknet.nl/qn/prive/e.edel/leloup/B457-4a_PRE_klein.jpg
For your example I would probably make 2 profiles: #1 one would be the basic shape of the railing and #2 would be the shape without the grooves. Then I would draw 2 profiled walls: profile wall #1 22 mm long (assuming the grooves are 5 mm) and then draw profile wall #2 through the profile wall #1 with 32 mm length. (or you could stick two bits of 5 mm on either side if you don't like the added linework on the top view, but really, at this scale that's never going to show noticeably)
You should end up with something like this (excuse the crude shape which does not do your design justice
😞
Added benefits of keeping it simplified are: lower poly-count in your model and no extra line-work in your elevations.
Good luck with your work!
edit: see you fixed it, I should learn to type faster
edit 2: made the first image a link, it's kind of big for the browser window
Erwin Edel, Project Lead, Leloup Architecten
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