Fillet error on both sides of model but not individually

[Anonymous]

I have run into an issue where I get a error when I try to fillet both sides of the model, however no error on either side indevidually.

Project File: http://a360.co/22rTQaJ

Error: There was a problem combining geometry together.
If attempting a Join/Cut/Intersect, try to ensure that the bodies have a clear overlap (problems can occur where faces and edges are nearly coincident).

[Anonymous]

I found the issue in the orriginal extrussion. I had selected a face that incuded some projected geomatry braking the continuity of the spline.