I'm having some very strange issues trying to use the planar command on an enclosed curve made of a couple arcs and polylines glued together with the join command.


I've got this curve here that I'm trying to make into a plane. It's fully enclosed, all one singular curve, and entirely two-dimensional:


But, when I try to fill it, or extrude it, I get this strange, inadequate approximation:


You can see here that the BREP is not being accurately represented by its sloping edge:


As you may have guessed, working with geometry like this down the line is next to impossible. This shape refuses to boolean or fillet. I have attempted multiple times to remake this curve with varying techniques, but have achieved similar results.

I've been asking a few questions recently, I'd like to take a moment here to thank everyone who responds to these. With that being said, Am I misunderstanding how solids work in MoI?
Thank you in advance.