Factual error: It seems unlikely Steve's bank or any bank would leave its vault open at night as they close around five or six.
Suggested correction: Steve is the bank manager and is closing up for the day. There is also a security guard sitting right by the door. And he has to unlock the door to let Al in. No mistake here.
The mistake is about leaving the vault door wide open instead of closing it. Not about Steve needing to unlock the front door to let Al in.
My point is Steve is closing the bank with a security guard there and the door is locked. So what if the vault is open? Steve just hasn't closed it yet.