In province 378, I set the culture of the province to be "seal", just like the culture of the provinces around it.
However, in the game, the culture of province 378 has changed to "fish" (both "seal" and "fish" are newly created cultures in my mod).
I've checked the error and it says there is no error in province 378. I've also searched for province 378 and confirmed there are no duplicates. Also checked the rgb and there is no error.
So may I ask why this is happening?