Today i tried this algorithm of patch creation and have problems with naked edges again.
Guess i missed something important in trimming process or in surface creation.
I assume that one of a steps should guarantee the right contact of result surfaces.
I just cant figure which one. I inspect the project you provide Michael. And it works like a charm.
So i recorded short video of whole process.
https://www.dropbox.com/s/8nms9s7buihvk56/2019-02-03_12-16-25.mp4?dl=0

I also add project file to inspect if necessary.