ASIO's $700 million building in Parkes Way has lost another panel, 12 months after the last one dropped off.
The fractured glass pane was visible on the Ben Chifley Building on Monday morning.
The building's monolithic glass facade has been a headache for the Department of Finance. It oversaw the complex's construction.
In 2012, at least 19 large glass panels cracked and fell to the ground from above the main entrance.
In February 2014, Attorney-General George Brandis said the Ben Chifley Building was unlikely to lose another $3500 glass panel.
A Department of Finance spokeswoman told Fairfax Media about this time that nickel sulphide inside the glass windows on the south side of the Parkes Way facade had caused the breakage.
Another spokeswoman confirmed on Monday the latest breakage was related to the same issue.
She said repairs would be done as soon as possible but the failure rate was "still within the statistical expectations for the amount of this type of glass that has been used in the facade".
The Department of Finance was working with the managing contractor to undertake the repair work.
The national spy headquarters was delivered two years late and $200 million over budget and its blueprints were reportedly stolen by Chinese spies before it was occupied, although the Australian Security Intelligence Organisation dismissed the hacking claims.
Malfunctioning alarms plagued neighbours in the leafy suburb of Campbell last year, forcing five federal government agencies to be called in to try to sort out the problem.
One neighbour complained to the Inspector-General of Intelligence and Security that the alarm ". . . continually goes off, often in the middle of the night waking our whole family and our neighbours".
"I have found it hard to find someone who actually cares about the problem as there doesn't appear to be anyone in the actual building when I have gone down there when the alarms are going off.
"This problem has gone on for the last year and must not be allowed to continue."