From what you say, unless there is a general statement in the Works Information along the lines of "any outstanding design not in this Works Information is to be completed by the Contractor" then, from what you say, I would side with the Contractor.
Having alerted you ?via an EW? to the issue, they can just do what the contract says. I.e. put in the door. If it doesn't stand-up, that's the Employer's issue.
Having alerted you ?via an EW? to the issue, they can just do what the contract says. I.e. put in the door. If it doesn't stand-up, that's the Employer's issue.