I would take a very slightly different tack. Send the owner a letter demanding that the common property walls etc be repaired and let them try to prove that it’s a building defect. There must be adjoining lots that don’t have these problems.
If they don’t respond, take action at NCAT including orders to access the property to undertake the repairs at the lot owner’s expense.
Be sure to keep ever scrap of paper and diarise every phone call that refers to damage from windows being left open.