Hello,

Here is the file. Yes, I am using the planar sections option. I originally thought that that unusual blend was happening because the connection point of the wing was pushed too far to the rear of the fuselage, and when that was pushed forward a bit that cleared itself up, but I started getting that unusual blend happening. The situation became a bit better when I limited the blend distance, but it began showing up again on other blended areas, and it really doesn't solve the issue at the trailing edge of the wing since that is a difficult surface to patch in. It does seem visually to flip right in the midpoint of the blend. Hope the file helps to see what is happening.