Yep, indeed already known and fixed for the public release tomorrow. It's an issue with the order the messages are viewed in. If you read Yukari's messages first (while still in the elevator), it gets unlocked as intended.
Thank you for mentioning it anyway, though. :)

Heh, we'll find out soon-ish what her thoughts on the matter are. Probably soon-ish, at least. I haven't written the content yet, so we'll see when exactly it happens lol