Causes for Crashing

What are the most common causes for crashing?
I'm having a lot of crashes lately, while I had none whatsoever in the recent past.

Can the amount of units in the map cause a crash?
What about level of the AI?
Buildings?

I had recurrent crashes on a custom-map with plenty of enemy towers and mortars, so I assumed too many things for the game to process, but I was playing a game right now with King enemies and the game simply crashed and I can't imagine the reason: I had discovered less than 30% of the map, even that part wasn't revealed (due to Line of Sight) and one of the enemies had just lost his hero to me.

Other than that, I can't think of any useful information to give.

So, again: what are the most common causes for crashing?

The only CTD I had with this version, was when an enemy used a map spell at the very beginning of a skirmish (can't remember which one). After army setup and loading, the name of the spell appeared at the map center as always, then it crashed. For the rest, I think it's the most stable version until now (at least for me)

Lurinth's Bow causes a crash and high level AIs have a higher chance of wearing it. Also AI heroes casting Summon Animal (nature magic) causes a crash.

Indeed it is a much better version, I rarely experience crashes.

Does the number of particles currently on the screen capable of causing crashes? The engine is old, I suppose that could also bring the game down, right?

Also, what is this about the spell name appearing in the center of the map? I never noticed this.

About the Summon Animal, is there something I can do, other than not playing against Druids? I see sometimes they summoning animals, but never realized that could cause a crash.

Is there some way I can edit out this problematic bow?

Indeed. Just edit items.xml found in English/Items.xcr

Thank you, I kept the item but removed every trait except for the Combat bonus.

Is there a way to edit out the spell as well? When playing single player, crashing is merely a nuisance as I can load it back, but in Multiplayer it is game breaking.

The spell is hard-coded I'm afraid.

No worries!
I will set the enemies' classes and avoid Nature Magic.

Thanks for the quick response!