Melodic Ideas in the Same Register
Ethnic references in the music can be a very sensitive issue. When they are stated inappropriately, it might quickly feel like a racist musical remark even though your intentions were purely to “localize” a character. In general, avoid scoring any sort of character just due to their ethnicity unless there is a really plausible reason for that.
Ethnic references for the portrayal of a certain location in the movie is less sensitive but even there you should in general be cautious. Using ethnic instruments or musical language is only appropriate if it is essential to the storytelling or to understand a character but should never be done just for the sake of doing it.