Hello,
So I finally tested a lazy fix that consists in setting veterancy to 1 instead of 0 at line 1987 of the script. It worked, I could play the mission normally up to the end.
I suppose it's not the way you might want to fix it, but those who want to fix the problem right now can do the same: at line 1987 of the script, replace "local veterancy = 0" by "local veterancy = 1".
Hello,
After many years I wanted to try again that awesome game and I wasn't disappointed 
However I encountered a bug on the first FA mission. I can destroy the Order basement and then protect the civilians, but then the map doesn't expand. The scenario keeps playing to a degree since I have to face a massive counter attack, but since the map didn't expand I can just stop it when it enters the combat zone. Apart from that the scenario stopped playing since no dialog is played and so on.
I was playing alone with the aeons on medium difficulty. Here is the log:
game_20354693.log
I had a quick look at the log and the script, it happens here:
I made some modding once ago, but it's been really long since then, so I'm not sure, but my idea is that veterancy = 0 (which is the case in easy and medium difficulty) is not a valid index to call CreateArmyGroupAsPlatoonVeteran. CreateArmyGroupAsPlatoon should be used instead or veterancy should be set to at least 1 in easy and medium difficulty.
I haven't tested yet (it's getting late here...), so take my analysis with caution, but hopefully that can help.
Don't hesitate to ask me if you need anything else to analyse!