'DetailCurve.ByCurve' giving error 'Curve is normal to projection plane'

I have a Dynamo script that until recently, worked as I had intended.

It’s set up to use a room boundary and an elevation view to create a perimeter line at framing for interior elevations. It’s complicated, mostly because I fight my way through Dynamo, but it was working, and now it won’t draw the lines I’m asking it to, and the error doesn’t make sense, because i can see that the lines are not, in fact, normal to the view plane.

I’ve attached a stripped model and paired down version of the Dynamo script.
DetailCurve-ByCurve Not Working.rvt (2.1 MB)
Int Elev 03 Automation_TESTING.dyn (122.1 KB)

If you open the model in the elevation view and run the script, it fails near the end:

I’m at a loss, and would appreciate any help. Thank you.