Hi Kev:
alternative solution:

make a BLEND G2 (bulge=0,5) between two main edges



extract ISOCURVES from blend surface



delete now blend surface than select isocurves+ four original edges and hit NETWORK choosing CUSTOM to have tight tolerance



now you have a Patch where main edges are G2 connected (NSIDED give just G1)

it's a compromise..i know...but you can't expect that tools work in all situations..this is a complex case (i attached my file)

M