Section 65 of the Strata Schemes Management Act provides authority to an Owners Corporation to enter into a Lot even without the consent of the Owner “in an emergency”. What constitutes an emergency is not defined but common sense should prevail. It might be reasonable to argue that if water is entering into your Lot from the Lot above and causing damage then the Owners Corporation is entitled to enter the upstairs Lot to rectify the problem.
So that doesn’t give an individual Lot owner the right to enter, but it does provide that authority on the Owners Corporation (or its agents, employees or contractors). In the case of an emergency you should immediately contact the Strata Manager or the Executive Committee.
Bear in mind though that an Owners Corporation is liable for any damage to a Lot of its contents caused in the exercise of this power (there is one excuse set out in the legislation) so at the very least the Owners Corporation would need to replace any broken locks or windows!