Population groups added on province gets wiped out when specific population civilization is bordering that country

[vendex_thegreatest 11]

 

To demonstrate this bug, im going to create a scenario in 5000 BC with population at 65,000 starting population and 32,000 starting economy.

Im going to pinpoint on this specific province, "Sapna". there is 26367 people and 5012 economy along by 0.24 development.

Now im going to cores, population and changing the province to 80% serbian and 20% bosniak.

Now that this is saved in, the population of the province "Sapna" Has dropped significantly, losing more than 20,000 population. The population still remain predominantly bosniak when its not suppost to, and montenegrins weirdly make up a significant minority of 20% of the province now. So what just happened? @Łukasz Jakowski

Please fix this bug as its destroying one base of the game that makes the game more fun for scenarios involving conflict.

Thank you for reading, and please help me get this topic to the developers of the game, or to get people in contact with developers to help out.