I have used ALL artillery either with one kind of gun or with different batteries.
I never had a CTD without artillery.
CTD occurs sometimes and sometimes does not reoccur on reload, the same army could do a battle without CTD and crash on next, using the same guns.
CTD may happen with mortar only and next time with volley gun only and next battle with same guns goes well.
Hard to find a guilty unit in those circumstances. It cannot be ONE faulty gun.
It never occured in a city assault, no matter how many different guns are involved.
Now if there was a trigger to a trait like "artillery commander" that was faulty it might be the problem, it would fit both conditions of randomness of CTD and involvement of artillery.
I am playing Hochland and using your version.