Just played Brazil for the first time, and I think I hit upon a bug. I was at war with La Plata and Chile, took Buenos Aires, forced La Plata to become my puppet via event, prompting them to join against Chile. A few days later I get an event about La Plata and Chile being at war, giving me a choice to either intervene or stay neutral. Presumably, this was meant to be a reaction to some event-driven La Plata/Chilean war early on which makes no sense in this context. A modifier to the trigger checking if La Plata is a Brazilian puppet should solve it.