Ian, first of all, sorry 4 possible mistakes from T9. Your theory is not showing exactly, why we are not in Meretrida, or Pergamon. We passed 3 systems, each having a fightable faction. At least, with election. My opinion it's just a bug. When rules are working 2 times normally, and another on the 3rd - there are not rules at all...
I was certainly surprised that it was Kopernik, too. My theory for that is that just as your invading faction has to be able to start a conflict, so does the faction you invade to fight. It would make sense, as the "no pending conflicts" rule was introduced to stop factions being in two conflicts at once.
Meretrida: the only non-native faction above 5% (or 7%?) there is UCA, who are already in a war elsewhere
Pergamon: Winged Hussars or Colonia Council. Both are recovering from Elections which ended on 27th.
Kojeara: Junkyard Dogs and Tenjin Reclamation are both native. Colonia Research Department has an active Election in Tenjin. Colonia Council, as before, recovering from Election. I guess Tenjin Pioneers could have been eligible - either their influence is too high or there's a rule that you can't attack the controlling faction with an invasion?
As the requirement not to have existing conflicts only came in during 2.4, and the only other case since then where the expanding faction *didn't* have a conflict pending is the ongoing invasion of Nomads into Tir ... this is of course just a theory.
EDIT: Actually, I've got a better theory for "why not Meretrida" - you retreated from there on 26 October, which is I think recent enough to be covered by the "systems you've previously retreated from are deprioritised for future expansions" rule, since you did start fighting Pekoe GA at only 4%.
Then Pergamon: Jaques and Explorer's Nation are still recovering from an Election, Galcop had a war until the 27th Jan, and Canonn had an Election until the 28th
Then the other Kojeara factions: PaX are in a war at the moment, and KoCK had one on the 28th.
So, that would make it:
Meretrida: eligible (Diggidiggi Mining Services) but deprioritised due to earlier retreat.
Pergamon: no non-native factions not pending, active or recovering conflict already
Kojeara: no non-native factions not pending, active or recovering conflict already (except for the controlling faction, and I think it's reasonable to theorise that you can't hit them directly with an invasion)
Kopernik: eligible, closest after the three above considered.
So on 17 Dec you had an Election pending in Mriya, got the Investment rather than invasion, and then your next expansion had the range to reach Farwell. This time, no conflict pending, so you get to invade.
