Bear in mind that the landlord probably doesn’t even know this is all going on. Far too many real estate rental managers see their job as being to protect the owners from any hassles or costs and push the rent up as much as they can.
What can you do about it? Politely tell them that you don’t accept either of these responses and that you will pay a reasonable rent rise based on CPI and that you expect a new oven to be installed as a fully functioning oven was part of your original lease agreement.
Otherwise, they can expect a call to NCAT.
If need be, find out who the owners is and contact them directly.