Slicing a curve generates a flat, not a complete curve

Hi - I’m new to Kiri:Moto but I think it’s great so far! I’ve run into a very simple problem, when importing from Onshape. I have a simple curved block (see below). When I slice it, Kiri:Moto doesn’t recognize the bottom of the curve as curved (see the path on the sides of the channel when ‘curves only’ is selected). I’d done this with and without “curves only.” Without “curves only” selected it will mill the whole bottom but will mill it FLAT, instead of contouring.


Here’s the shape in Onshape: