@Ryuz4ki
Sorry for the issue. Good post, this is information I need to look at.

My first thought is, you are using mods that are not compatible with one another.
Formable nations is not compatible with Contest Europa. They make changes to the same files.

I'm not familar with Knights Templar, but I would guess there is a compatibility issue there too.

Contest Europa is a hard mod to be compatible with if you want to use mods that add other nations. You really need to rewrite the other mod to make it fit into the CE format.

The bug you are experiencing could easily be the result of a mod conflict.

One way to test for sure is to look at the error log immediatly after you get a crash like this.
Documents\Paradox Interactive\logs\error.txt

You may find the issue there. The document resets itself after the game closes each time, so if you have played EU4 after the issue it will not still be there.

This isn't the answer you are looking for but I would say it's just a mod conflict. There are other mods on that list that I don't know very well and could cause a problem as well:
Matts Natural Disasters (no idea)
Reduced Core and Annexation Cost (no idea, but probably fine)

If you have some idea of what you are doing I'd say open these mods up and look at their decision folder to see if there are any file overlaps with Contest Europa.

@Ryuz4ki
See if you still have the same issue with the new version of Westernization Reworked. I did not update on Steam and that will cause all kinds of issues.

I have a similar problem (so i figure opening another thread would be silly).
As for Ryuz4ki the game freezes then crashes after no particular event, but always on the February 21st 1745.
I also noted that if i disable this mod and then load the save it doesn't crash but i can't select any unit type and it converts all my army in infantry with 0 pips.
I am playing as Hungary and i'm using these mods:

"AA CE - RC Compatibility Patch"
"AA Contest Europa - Religion Addon"
"Armies Reworked"
"Contest Europa"
"EVE Religion Lite"
"Historical Events Extended"
"Organic Culture Transmission"
"Reworked Cultures"
"Rosetta"
"Ruler Titles [XVI.0527]"
"Ruler Traits Lite"
"Westernization Reworked" (the new one you talk about)
"aa Recolored Nations - More Ship Names Mod Compatibility Patch"

And i don't know if it helps you but here's the error log:

[localize.cpp:523]: Localization file 'localisation/education_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/education_l_english.yml
[localize.cpp:523]: Localization file 'localisation/rt_dynasty_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/rt_dynasty_l_english.yml
[localize.cpp:523]: Localization file 'localisation/education_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/education_l_english.yml
[localize.cpp:523]: Localization file 'localisation/rt_dynasty_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/rt_dynasty_l_english.yml
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_1 already exists with version 5. Set a higher version on entity RFR_CAVALRY_1
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_2 already exists with version 5. Set a higher version on entity RFR_CAVALRY_2
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_3 already exists with version 5. Set a higher version on entity RFR_CAVALRY_3
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_4 already exists with version 5. Set a higher version on entity RFR_CAVALRY_4
[persistent.cpp:44]: Error: "Unexpected token: leather_cannon, near line: 342
" in file: "events/HEEMaratha.txt" near line: 342
[id.cpp:78]: Failed to create id 40900001 53. Already exists in game.
[id.cpp:78]: Failed to create id 41200001 53. Already exists in game.

Thanks anyway.

Originally posted by Fililippo:

I have a similar problem (so i figure opening another thread would be silly).
As for Ryuz4ki the game freezes then crashes after no particular event, but always on the February 21st 1745.
I also noted that if i disable this mod and then load the save it doesn't crash but i can't select any unit type and it converts all my army in infantry with 0 pips.
I am playing as Hungary and i'm using these mods:

"AA CE - RC Compatibility Patch"
"AA Contest Europa - Religion Addon"
"Armies Reworked"
"Contest Europa"
"EVE Religion Lite"
"Historical Events Extended"
"Organic Culture Transmission"
"Reworked Cultures"
"Rosetta"
"Ruler Titles [XVI.0527]"
"Ruler Traits Lite"
"Westernization Reworked" (the new one you talk about)
"aa Recolored Nations - More Ship Names Mod Compatibility Patch"

And i don't know if it helps you but here's the error log:

[localize.cpp:523]: Localization file 'localisation/education_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/education_l_english.yml
[localize.cpp:523]: Localization file 'localisation/rt_dynasty_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/rt_dynasty_l_english.yml
[localize.cpp:523]: Localization file 'localisation/education_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/education_l_english.yml
[localize.cpp:523]: Localization file 'localisation/rt_dynasty_l_english.yml' should be in in utf-8-bom encoding
[pdx_localize.cpp:847]: Missing UTF8 BOM in localisation/rt_dynasty_l_english.yml
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_1 already exists with version 5. Set a higher version on entity RFR_CAVALRY_1
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_2 already exists with version 5. Set a higher version on entity RFR_CAVALRY_2
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_3 already exists with version 5. Set a higher version on entity RFR_CAVALRY_3
[pdx_entity.cpp:2151]: Entity FRA_CAVALRY_4 already exists with version 5. Set a higher version on entity RFR_CAVALRY_4
[persistent.cpp:44]: Error: "Unexpected token: leather_cannon, near line: 342
" in file: "events/HEEMaratha.txt" near line: 342
[id.cpp:78]: Failed to create id 40900001 53. Already exists in game.
[id.cpp:78]: Failed to create id 41200001 53. Already exists in game.

Thanks anyway.

ehem, it crashes after THE ARTILLERY DISCOVERY EVENT xD dude please read it again

@Ryuz4ki
You are good now right?

@Fililippo
Are you still having the same problem after updating to the newest Westernization Reworked? That hopefully solves your issue.

Side note, your error log tells me you are using some mods that are outdated and require updates.
[localize.cpp:523]: Localization file 'localisation/education_l_english.yml' should be in in utf-8-bom encoding
This means that the mod author hasn't updated the mod for 1.17 format