请教小白兔及各位高人, 父母移民background check...

My parents went to Guangzhu for 移民 interview. The officer didn't ask too many questions, just collected our tax return forms. And then he told them that there is 1 step of inside background check forgot to do, asked them to go back and wait for further notice. What's this inside background check (he said it will take around 1 month)? They already did background check before sent out interview notice. Do my parents need to do 移民 interview again?