Cause of CTD: Dividing by... zero?

[Evanescent]

I've come back to Shogun 2 after a considerable hiatus.
I had an old mod of mine that I used to play, so I decided to see if it still worked. It does--mostly, until a random CTD happens.
I tried debugging, and apparently, the game crashes because it's trying to divide by zero.

Now I noticed that this happens when an AI clan moves its army towards a castle, and I have no bloody clue where in that process the game tries to divide anything by zero. I've looked at all the variables in my db files(the mod was created using PFM), and there's nothing amiss. No weird numbers, no typos, nothing. I think I checked all the potential culprits in data files that have anything to do with the campaign map.. but the crash keeps happening.
So I was wondering if anyone has a clue what could cause this try-to-divide-by-zero-then-the-universe-crashes-around-me issue... if anything, a suggestion would be most appreciated.

EDIT: Actually, after a reinstall and more poking around, I discovered that this seems to be a very specific problem. Every other castle town in the game seems to be working fine. It's Hida that's causing all the CTDs. An army approaches Hida, tries to attack it, the crash happens. Apparently that's where dividing by zero mishap is happening. I have no bloody clue what's wrong there though... I've taken out all the campaign-related db files out, and it still happens.