Too stubborn AI?

[Doomdark]

I don't know why but the AI is very unpredictable in these matter, especially when it concerns overseas provinces. I remember that in my last game as India, being a westernised Asian, I was in a very convenient position to dominate Africa. Unfortunately, Castille had already occupied 7 very rich provinces in Eastern Africa (just below Swahili, I think). I attacked and captured all the 7 provinces and had to wipe out a few Castillian, English and Portuguese navies and armies. I didn't even once cross the coast of south Africa. And yet, Castille easily acceded to my request for ceding all the 7 provinces. I did the same to Portugal later. Twice.

The AI is less stubborn about colonial provinces, to make colonial wars possible.