"They have their own interpreters."
Translation:De har sina egna tolkar.
If I remember well, deras vs sina follows the same logic than hennes vs sina : is the person owning the object is already cited in the sentence, it is ok to use sina. Else, you have to use hennes / deras. Since "hennes" is right in any case, I expected "deras" to be right also, and I don't understand why it is not