Oh, sorry, I guess I could have worded that a little better. What I meant was that if you got past the area with the Fragile Key without getting it, then you're on one of the routes that doesn't need it.
If you got to where I think you did (NW corner?), then yeah, that's the toughest part of the puzzle. But the multiple routes exist, in part, to let you bypass some things by thinking a little outside the box.
Was it the far NW corner you wanted some help with?