I posted about this a while back and got no response, but now there's an actual Technical Support sub-forum perhaps I'll have better luck.
The 'Immigrants' colonial action seems to reduce the population of provinces in South-West Africa to zero rather than increase the number of people there. These were provinces with only 1 population to start with, so what I think is happening is that the card is correctly reducing the native population by -1 (to nothing) but is then failing to add the +5 population of the colonial power's ethnicity.
Hopefully if and when PoN gets another patch this can be addressed. Is there any work-around I can do in my current game to edit the province population to what it should be? (I'm not an expert on the AGEOD game engine or file structures, so I'd need fairly step-by-step instructions, I'm afraid.)
Thanks.