It's been closed again after a report confirmed the tower's bell structure flunks new standards.
The Culture and Heritage ministry's Te Pae Mahara manager Brodie Stubbs says engineers suggested the report after strengthening work in 2018.
He says the tower was given some reinforcement, then reopened.
He says it was strengthened despite not knowing what the building's safety standards actually were, then reopened to the public.
He says there was the opportunity to quickly and cheaply add steel to the seismic bracing, but it wasn't done on the basis of any official report.