What I would like to know is whether the couple had a professional building inspection report carried out. If, as I suspect, they didn’t then they lost the opportunity to refuse to complete the purchase contract until the defect was rectified. of walking away from the purchase.
Here I make a second assumption that the law in Victoria is the same as the law in NSW when it comes to building defects. That is, waterproofing (or lack thereof) is a major defect entitling a purchaser to refuse to complete until the defect is rectified.
The moral of the story is that when purchasing a new apartment, obtain a building inspection report before settlement.