I am trying to figure out what determines the random skill you get from rare factor combination. If you just reload the save and try again, you will get the same skill. However, this can change if you do something else - like combining with another unit. This change can persist if you reload the save (meaning, you won't get the skill you got at the beginning of this whole attempt). But its also more than this.
For example-
Save 1
lets say I get infinite bomb, a super OP skill (kills anything in 1 hit)
Save 2
I want to try and get this skill on another character., so I reload to save 1. Normally, if you just reload the game and attempt rare factor combination on another character (doesn't matter the unit types), you will get the same skill. So the game keeps track of this. In my case, I realize that I can't get it work with one combination, I need to do two combinations. So I do some stuff, may be combine one unit with another, and the results change - I can no longer get infinite bomb, instead I get the battleship skill.
Reload back to save 1
I attempt combining again to get infinite bomb, but I still get battleship. What gives?
Reload back to save 1
This time I give one unit a ractor factor scroll, and try combining again. This time I get infinite bomb again.
The only reasoning I can think of, is that there is a counter of sorts. If you do certain actions, like spend a turn, or combine with a unit, or give a unit a scroll, or have a character event, then this counter moves and you get the next skill in the list. And this persists if you reload for a second attempt immediately (Without doing anything else)
But yea, I would appreciate if someone else could shed some light on this.