Changing Diplomacy desync/crash?

I was playing a Diplomacy (Europe scenario) game. I changed Diplomacy with someone and then the game desynced instantly. (or crashed) Has this ever happened you before?

Before hand I also changed diplomacy to ‘ally’ just fine during the game. But when I tried to set to neutral with someone it crashed.

I tested it again in singleplayer. This time no crash. Maybe someone crashed the game, and it wasn’t my fault?