Yes, Jimmy-T has the right information. But it’s not possible to know whether your rental agent or the strata manager, or the strata committee, or a combination, is the cause of the lack of a suitable response…
As a strategy to ensure that the problem is dealt with quickly, you should be raising the problem with the building’s strata manager, directly, and CC them in with your correspondence. (You can normally find out who is the strata manager using the NSW Strata Hub enquiry database for your building.)
Another important strategy is to use the magic words in your correspondence about the broken intercom and security system, which is that it is a “health and SAFETY” issue. A faulty intercom and lock on the building is a “serious safety and security” problem, and you should stress this in all correspondence. Nothing worries a rental agent or strata manager more than them delaying dealing with a security and safety issue – and this is one area where a strata manager can overrule a recalcitrant strata committee and arrange urgent repairs. So continually remind the agent and strata manager that the faulty security and intercom system is a serious safety and security problem, because if an ambulance or police were called to your Unit there would be no way for them to get access to you.
Also, to add some encouragement to the rental agent to act, request that the agent provide you with a rent reduction while the fault exists. The law firm Muellers states that in NSW, landlords must legally provide a property that is reasonably secure. If broken common area doors increase security risks or cause daily inconvenience, your landlord is breaching this duty. They can claim the lost rent back from the Owners Corporation. So both parties will have a reason to fix the problem, as both are at fault and will be out of pocket.
The agent has to take the request for a rent reduction to the owner, who will also have reason to pressure the OC to fix the problem, and also to prod the agent into action as well. But gather evidence of the problem, such as dates and time, and photos, and keep a record of visitors who could not contact you, to back up the request…
Remember that a “safety” issue is a red flag to Owners Corporations, agents and strata managers, and if your problem (reasonably) involves a safety problem, this escalates the speed of the response significantly.