Some guesses:
A missing or a damaged file.
A my/me/you pointer (unwillingly) instead of a PARTICLE in a particle function/ event function - I've once helped finding a seemingly random "acknex.exe has stopped working crash" in a bigger project. That was the reason.
You are overwriting some memory somewhere, for example in a loop and an array where you go one step to far, or you have for instance my_array[i] = ...; somewhere where i can have any value because you wanted to write my_array[num] instead.

I'd say create a copy of the whole game folder, then delete files and content and maybe even script, write diag(...) and the like everywhere and check if the crash still appears. If it doesn't use a previous version/ copy and delete less stuff, like in the mathematical interval halving method.