This post is a summary of all the possibilities for crashes I collected so far:

If your game crashes right after starting you probably have too many mods installed. Having a high amount of mods (something like 16 or more) installed can make the game behave very weirdly. I would need to uninstall some mods.

Another reason could be the following steam bug. Sometimes, steam workshop mods can only use a fraction of your total RAM available, for this to fix you need to move the mod from the workshop folder to the normal mod folder:

Go to the folder where steam workshop mods are stored: ...\Steam\steamapps\workshop\content\48700, there copy the file called 1612746028 (this is the mod folder) and move it to ...\Steam\steamapps\common\MountBlade Warband\Modules and maybe rename it to something like "Aut Caesar Aut Nihil 2" and select this in the launcher. Though the mod wont update automatically any more. Once the mod updates you need to repeat this process again.


If your game crashes when loading a save, the save file is probably corrupted. I always recommend to have multiple save files so that you can go back to a previous save if it should happen.
Though you can also try to restore the save file:
The game generates a backup of the last save. Head to the savegame folder of the mod, this is under \Documents\Mount&Blade Warband Savegames\Aut Caesar aut nihil
there search for the file called last_savegame_backup.sav. This is the save backup file. Rename it to something like sg00.sav (this is the name of the first save game slot, sg01.sav would be the second one etc). Start the game and load the save, if you are lucky it works

There are two kind of crashes: First one is you receive an error message: Run-time Error. Second one is you receive no error message and game just closes. I list the ones which are most common for runtime errors:
*) Your PC has less than 4GB RAM, hence game runs out of memory
*) Game allocates more than 4GB RAM (the engine is only allowed to take 4GB, hence it crashes)
For non runtime errors it is usually:
*) issues in the code
*) meshes with many, too many vertices
*) Antivirus software is not allowing the game engine to allocate RAM

The point about the Antivirus software can be resolved by temporarily disabling it while playing the mod. (I myself had this issue too. I changed the Antivirus software, as it was not good anyways, which then resolved the issue.)
I basically tried hard to improve meshes, reduce textures by removing unnecessary or unused once. Nevertheless, I noticed the following on my notebook: After I played a large battle (2000 vs 2000) on largest battle size and I enter other large towns (like Alexandria, Rome, Antiochia) game will crash. Because the large battle is basically overloading RAM. So to clear RAM, I save after such a battle and just exit the game and then restart. Hence no crash will happen as RAM has been cleared due to the restart. An example of how to avoid crashes: Before a major battle save the game. Exit the game and restart the game. Then play the battle. Then save and restart game again. By restarting the game you clean the RAM. So its a good idea to restart the game whenever you make a short break.

Here is a list of things you can try to reduce RAM usage:
1) In launcher check that you have disabled the edit mod and antialiasing.

2) disable sound variation: in launcher under Configure => Audio => disable “Enable Sound Variation”

3) Disable music in launcher settings: in launcher under Configure => Audio => disable music. (if you just set music volume to zero in the in-game settings the music files are still loaded by the engine, you are just not hearing them, so to save RAM disable them in the launcher settings)
This is a must if you do not listen to the music anyway. If you like to listen to the music of the mod you can instead play them in the background, using some music player. The music files are stored under: C:\Program Files (x86)\Steam\steamapps\workshop\content\48700\1612746028\Music
Of course, if you just play them in the background you wont have situation depending music.

4) Enable “force single threading” and see if it helps. If it is already enabled, disable it . I do not know why but during the tests on my notebook it indeed also effected RAM usage.
If everything should get worse, its may worth to take a look at this thread for more information about how to make warband use multiple threading better: https://steamcommunity.com/sharedfiles/filedetails/?id=2069289874

5) Decrease battle size and decrease corps limit

6) decrease texture resolution: start with setting it to 80% first and if necessary lower it further. (This is probably the best way to address runtime errors. Though I would not go below 50%. 75% are still looking good enough but everything below 50% becomes ugly)

Also here I want to list some other settings I recommend:

In the rgl_config.txt file (under documents/warband) I use the following settings:

render_buffer_size = 16 ##you can try to increase values, like: 32,64, 128, 256 or even much higher values like 1024, 4096, 8192, 16384
As it seems increasing render_buffer_size to high or very high values can help fixing runtime errors but also stuttering and fps drops. Though on some pcs you can get glitches when you set the value very high.

max_framerate = 120
use_pixel_shaders = 0
use_vertex_shaders = 1
fake_reflections = 1
use_ondemand_textures_ = 1 ##may try 0 if you have CTD
use_ondemand_textures_mt = 1 ##may try 0 if you have CTD
antialiasing = 0
force_vsync = 0

In the in-game graphic settings I use the following:

shader quality = high (important for better look)
HDR mode: OFF (not longer strictly necessary, but I still recommend it, though now it is matter of taste or performance)
Auto-exposure = disabled (not longer strictly necessary, but I still recommend it, though now it is matter of taste or performance)
depth effects = disabled (not longer strictly necessary, but I still recommend it, though now it is matter of taste or performance)
instancing = disabled (not longer strictly necessary, but I still recommend it, though now it is matter of taste or performance)
gras density = 30% (gras is per default very dense)
realistic shadows on plants = full (no longer strictly necessary, but I still recommend it)
tree detail = high
tree degrade distance = 60%
character detail = slider value is in the middle
character shadow detail: slider value is in the middle
number of corpses = 0
number of Rag Dolls = 0
Blood stains: near player only
dynamic lightning = enabled
character shadows = enabled
environment shadows = enabled
particle systems = enabled
Anisotropic filtering = enabled
fast water reflections = enabled