Trimming after Extracted Isocurve deformed surface

Hi i have a problem i’m not sure why occurs.

I have two filled edges that overlaps, and i wanna rebuild this part to make a smooth transition.

But after cutting the sektion, one of the surfaces deforms, enough so that i cant join them after. I think my method is okay?

Where the two fillets overlap i ExtractIsocurve.

And trim of the part

Then use sweep2 to rebuild the section

But after this the pieces don’t match anymore.

The Isocurve is still in the right position but the trimmed surface have deformed.

110319.3dm (3.9 MB)