Split Errors Using a Surface

heep_xj

I'm trying to trim the edge of this airfoil to a very specific shape, where the bottom half has a seamless fit, but the top goes into the side support of the spoiler. I intend to cut the airfoil with the surface that's pictured. To create the surface, I cut an intersection curve in half, then used 3d fit splines to make it go into the side of the spoiler. After that, I filled them to create a surface.

Based off the visuals it's giving me, it seems to have successfully split it, yet it gives me an error. Any help would be appreciated. Thank you.

Front view of what I'm trying to do.

heep_xj

Oh, and here's the file.

https://cad.onshape.com/documents/4af87449027adba466b81dce/w/2b49521571d916b149485b68/e/ab84d502cd82b1ca4db37b72?renderMode=0&uiState=66744d5d7e9a9e0c15c244b3

eric_pesty

I would try to see if extending the cutting surface (so it's bigger than the face it's cutting) helps. Rounding errors in the math could make it appear like it's not completely cutting the part.