[sgqwonkian]

And the answer is...

...something totally unrelated, I guess.

It crashed like 7 times in a row on the right-hand mission, but loaded fine on the middle mission 3 times in the midst of that.
I thought it was something wrong with the last third of mission.ini. So I copied the middle third to the last third.

Crash on right-most mission. Huh? Why didn't that fix it?

Tried the middle mission again - and now it crashes.

So I pulled the whole mission.ini file and run it with just the normal missions.

Hangs for 20 seconds on the right-most mission, but doesn't crash and eventually generates the univers.
Try again (still on right-most), no hang this time. Seems fine.
So now I try the middle mission, and it crashes.

Grrr!