Hi Anthony, yeah the part that's particularly difficult here is the mix of different proportions within the same surface, since that little radius pushes out with the sweep to a much larger length than that radius in the sweep direction.

That means you've got a surface fragment that is like a long very thin sliver - things like that will cause some particular difficulties, particularly with stuff like join, since with a slivery surface like that both of its long edges may be within tolerance of the other piece you're trying to join it to and it's kind of easy for it to be basically treated as if it was a degenerate collapsed line without any surface area at all.

So anyway, this mix of different proportions within the same surface is particularly difficult - if you had something like a tiny part that was all made up of surfaces that were also of the same proportions that would probably be a lot more feasible.

- Michael