I don't think I need to open your files to help.
Delete all contacts in the Connections folder. If you use Share Topology, you don't need them.
You have to do a Sweep mesh method on only one body for the manual source face to be available then you can Inflate this method and choose the boundary edges on the selected face.
I just wanted to understand perfectly the sweep method. In this post, you said that you can't use sweep mesh method with manual source face when you select more than one body.
But it is possible. In this part, it works. I tried to create a new part tallest than the first one and this time it doesn't work. I'm feeling frustrated because two same parts but one work and the other don't... illogical.
What is the "rule" behind this?