The desolate new headquarters of spy agency ASIO has lost another expensive glass panel.
A tall pane almost four metres high broke last month on the building's top floor.
A spokeswoman for the Finance Department, which is overseeing the complex's construction, said the glass ''shattered into small pieces but remained in place and was removed manually''.
An exclusion zone was set up and the ACT's work safety authority was notified.
The $700 million office block - a vast arc of glass that overlooks Lake Burley Griffin - has been plagued by problems with its windows.
About two years ago, 19 of the panes, each of which cost $3500, ''progressively failed'', according to the department, and fell off. The area was evacuated before the first sheet fell. No one was injured.
But the incidents delayed construction by weeks, which helped push several building subcontractors on the site into insolvency.
The windows that fell in 2012 had not, at the time, been fixed permanently to the building. But the latest pane shattered even though most aspects of the headquarter's construction finished months ago.
The monolithic office - Canberra's largest - was formally opened in July last year, and many of the intelligence agency's 2000 staff were expected to move in two months later.
But it remains empty, and ASIO is unsure when it will move in.
The project, which began seven years ago, has been beset by problems, which helped inflate its costs from an initial estimate of $460 million.
In 2011, a teenager breached the secure construction site and fell nine metres into a basement, where he lay unconscious for 36 hours.
The building's blueprints were also stolen, allegedly by Chinese hackers.
None of the workers who helped build the office can discuss its troubles publicly, because they have signed confidentiality agreements.