Is mod_debug.txt a file in my games files? And it happened twice now while playing revolutionary France.
Yup, it's supposed to be in /log/mod_debug.txt in your FtG root folder. It tell what what pictures it is using for actions in the game. history.txt tells you which events successfully completed, so if your crash is due to an event you won't see which one AFAIK.
Here my suggestions:
Maybe it should tell which event loaded and wheter it complete. That way if an event crashed your game you'd see something like this:
April 4, 1428 loaded event #13371337: Zhang He discovers America
April 4, 1428 done with event #13371337
but if it crashed you'd see:
April 10, 1428 loaded event #13371138: MXXXIV Monthy Python Philosopher Games
and you wouldn't see the done line - so you'd know that event was probably the reason for the crash.
And something similar for savegames/scenarios:
loading country caricom from savefile.eeg , so you'd have a better idea of what country crashed the game.
It is just a matter of printing out the arguments passed out to select C++ methods in a log file.Also if you are a modder you'd just have to ask the user to send you this file, and your odds of finding the bug would be way improved. If you know the culprit is country XXX from your 1419 scenario you only need to look at maybe 50 lines compared to all the files in your scenario.