I've found a million problems with colonization. Decisions don't work for no good reason. Some areas can't be upgraded into protectorates for no good reason. I can't imagine this area of the game was tested much, probably because it happens later and it took too long to get there. But without it fix...

I posted about this on the Paradox forums. I found that same thing happened in a S-P game trying to annex Tuscany. They accept the peace deal giving up their one province. They get peace, and they get their province back as if nothing happened. I'm guessing it's a problem with peace deals that give ...