I've noticed a few times now having restarted Fed playthroughs half a dozen times since getting this mod, that a few events seem to always happen, but they don't always resolve themselves the same way.

-Terra Nova seems to have resolutions where you rediscover the Novans and they form a colony for you, and sometimes you don't and there's no trace of them.

-Xindi event chain has several of these. Sometimes researching a cure for the vulcan ship results in saving them, sometimes it results in not saving them. Sometimes accepting Shran's help results in the Kumari turning up at the final leg of the event chain to save earth, sometimes not.

-Events like the Second Chances one can end with the duplicate dying, sometimes living (but not sure what is supposed to happen here?).

-Silent Enemy has some variability too, with the ship disappearing completely or (as happens in my latest playthrough) actually communicating with you if you hail them.

My question is what determines the variability? Is it completely random chance, or are there conditions that are being met (or not being met) that aren't being communicated?