If Mason patients need to go to the toilet overnight, they alert staff with a buzzer and are let out.
The Waitemata District Health Board, which runs the clinic, says Dame Beverley's recommendation raises issues of staff and patient safety - and staff numbers. Clinical director Dr Jeremy Skipworth said his clinic had moved away from blanket locking to a more individualised approach based on the assessment of risk for each patient.
But complex issues remained on whether more doors were left unlocked and what that meant for increased staffing needs and everyone's safety.
The Public Service Association declined to comment.
Dr Skipworth said many of the patients had come from New Zealand's highest security prison, at Paremoremo, where cell doors mostly were kept locked.
"We are dealing with a population who, for reasons not just of their mental illness, are regarded as high-risk individuals. There's no other forensic unit in New Zealand that takes as many people classified as maximum security prisoners as we do."
He said the clinic was legally obliged to provide a safe environment for its more than 100 inpatients and 450-plus staff (some of whom worked off-site).
One of the higher security units would need wiring of electronic locks in bedroom doors. He expected that, except for that unit, the clinic would comply with Dame Beverley's recommendation over the next few months.
The ministry's director of mental health, Dr John Crawshaw, told the Herald that although it did not support blanket door-locking, it recognised that where it had occurred, it would take some time to make changes.