We could see a repeat of 1975 which resulted in the dismissal of the Whitlam Government.
Anyway, why it could be unstable?
Well, Labor party MPs must follow along the party line when it comes to voting on a bill whereas the Liberals, Independents and Greens can vote whichever way they want on a bill.
So the independents allied with Labor can decide to veto or nix a bill and Labor needs them to get enough numbers to pass the proposed bill.
The Independents are the one who holds the balance of power and if they're not happy with their allies then they can cause trouble or become rather demanding, thus forcing Labor to give more grounds than they wanted.
Also because of no majority, it has the potentials for many bills to be blocked in both houses. If a series of bill proposed in House of Representatives and the Senate are rejected repeatedly. And if there's no vote of confidence in the Government then the Governor-General (the representative of the Queen) will have to decide to dismiss the Prime Minister and its party and call for a new election....
I don't even know who's the deputy Prime Minister. No doubt one of the Independents will want that role.
Do you understand better now?