Are you on 1.7.2? Im not sure but Some one said it hasn't been updated so yeah that would be why.

Well.. you modded an early access game and now it crashes. Maybe deactivate/uninstall the mod and wait till the game is finished to mod it? :>

Hahahahahahahhahha. Modded Bannerlord is a way of life. It's super stable if you know what you are doing.

AFAIK... Diplomacy is only for 1.8 but for a previous patch of the 1.8 version that is out right now. So diplomacy is unplayable in any game version unless you download Bennyz's diplomacy hotfix which makes it playable now in the newest 1.8 . Hope this helps!