If I read under >tools > commands the the attached file in Rhino 3, the function _NetworkSrf sorts the curves and creates a surface. If I do exactly the same in Rhino 5 the script terminates and I get the message "Unable to sort curves. Select curves one at a time." What is different in Rhino 5, that it fails to do what Rhino 3 can do?
Also, just FYI, you can use _SetRedrawOff at the start and _SetRedrawOn at the end to speed things up, and _noEcho at the start as well, to minimize the command line printing.
Since the same issue exists when I use _NetworkSrf manually, the trick seems to be to first select all curves and then click on "Curve Network". The other way around - first click on "Curve Network" and then select all curves - does not work manually either.