If you changed some splines then you probably moved or deleted something that had relations to the later features. Your Surface-Plan5 sketch has a lot of dangling relations from other geometry that no longer seems to be there.
Thanks for your quick answer !
Here is a new version I made.
First, I don't think it deals with broken relations since it won't smooth between sketches even without the guide (purple) splines I told I had changed (sketch 3D10). And I have no errors now.
I know for Surface-Plan5, I changed it, but the thing I want to smooth is before Surface-Plan5.
My explanations aren't enough precise... Let's retry.
On the new model, I have Surface-Lissage15 which works. I would like to have a second Surface-Lissage which is almost the same, using the other contours on the same sketches (sketches 11 and 41), just before or after Surface-Lissage15, and with the 2 hooks on the back.
Base V3.SLDPRT.zip 776.8 KB
It looks like you should take a slightly different approach to this. Instead of trying to do the whole profile in 2 moves, I broke it down in 3 moves to get the surfaces you are looking for. I did this with 2 loft surfaces and 1 extrude surface. Because of some anomalies I had to trim the ends of these surfaces to everything to knit together and make a solid.
I am running 2017 so I cannot send you my file but included this nice picture instead.