Check the attached file. I tried to shrink that surface, but for some reason Rhino 7 refuses to do so. 
I’m aware that I could use ! _RefitTrim as an alternative, but it will change the distribution of the control points, so the ! _ShrinkTrimmedSrfToEdge command is exactly what I need. But it fails. Is that a bug?
Rhino 7 refuses to shrink this surface.3dm (195.2 KB)
Not a bug. At the corner in Pascal’s image there is not room for shrinking. The end of the untrimmed surface edge coincides with the end of the trimmed surface edge
Thank you for pointing out that, Pascal! For some unknown reason I was blind enough to not see this area. 
Wow, I have to be more careful with observing the surfaces. I still can’t believe that I was unable to notice that simple fact. 
When I do this, I go off and make a coffee.
-Pascal
Good idea! 
Maybe it’s time to make a break for today. it was too much work already.
