Arverni CTD when destroying Romani

I'm playing as the Arverni, and the year is 238. I am experiencing a persistent CTD when annihilating the Romani. The situation is this, I have the last Roman city, Rhegion, besieged with no FMs inside. The last FM, the leader, is outside near Taras with a small army. Every time I kill the faction leader in a battle, the campaign will CTD the moment it returns to the campaign screen as it tries to process the destruction of the faction.

I've fought four different battles, thinking it had to do with the location or something. I've fought him in the field in three locations, autoresolved once so he retreated to Rhegion, and then allowed him to attack my besieging city and killed him in the reinforcement battle that followed, all with the same results. Regardless of location, forces engaged, the presence of reinforcements, the season (the battle ranged from the winter of 239 to the summer of 238), all cause a CTD as I kill the last FM.

Any solutions? Otherwise I shall have to abandon my Arverni campaign because the only way to solve them would be autoresolve which is way too bloody for my minimal-casualty style.

Have you tried taking Rhegion first and then kill the FM after he's turned Eleutheroi?

Yeah I just thought of that possibility. Though I had been hoping to avoid assaults. My campaign has been playing with a pseudo-house rule that prohibits assaults. But if it must be done, it will be. Shall try it, and post the results.

Could you please post your savegame before the battle that leads to a CTD? Does auto-playing it with auto_win and destroying the Romans work?

Are you using any BI options?

I haven't tried the autowin thing, but I did try the suggestion to storm Rhegion. The FL turned eleutheroi without any side-effects, and I killed him easily.

...how do you upload the savegame?

https://forums.totalwar.org/vb/showthread.php?t=80870

Perhaps it's a trait-related problem if it is the FM causing the crash...

After all your campaign isn't broken if you bend your house rules and attack Rhegion ;-).

http://uploaded.to/?id=vr8hth

here we are. This is the turn in which my army was about to attack the Roman faction leader's army at Taras. The second army is besieging Rhegion.