I finally conquered the last holdout province on an expert campaign with Takeda. I lost my daimyo in the battle because I was answering a text message and he got jumped by reinforcements. After the battle I'm informed that my new son has come of age and it turns out that he's my new daimyo. I didn't notice this at first because I was clicking through the announcements as 30 provinces rebelled. They've all got what looks like 3-400 men in each one. It's a bit galling because every province has 4 shinobi in it and loyalty above 300%.

I'm not sure if I've just been given a new challenge or been screwed by the game.

Has this happened to anyone else?