I had a heck of a time finding sector 5. The only thing I can say is that it was after sector 02, and I had just upgraded my Aftcastle to Invincible when I finally found it. I had been rocking Invincible/Bronco/Invincible/Bronco for five or so attempts with absolutely no luck until I made that change. It's still probably voodoo, though.

Meanwhile, I've found a new sector on every one of my last voyages (5-8) with the same equippage.