It might be a bug...
I had the same thing happen where someone's info checks out, but when you call their apartment to double check, they answer and say they're inside
But since all their info checked out, I opened the door for them anyway, hoping the endgame breakdown would tell me what I missed, but then I survived with 0 dopplegangers allowed in!
Either it's a bug, or the residents are supposed to make mistakes sometimes, so you can't just take their word for everything