(QLD) Retaining wall - who is responsible for cost

I'm not sure THAT timber is fine. Thin boards ? Should be min 50mm but ideally thicker. H3 ? H3 isnt suitable against earth. H4+ is min timber spec. Moisture and pressure may bow that too and the fence panel distances are too big for timber retaining and only reason they chose the intervals was for the colourbond panels widths. Concrete sleepers would have been wiser and when you look at the posts you must use to install them it gives no comparison to using a colourbond milled fencing steel post in its place. ...Of course it costs more !! I will also bet there is no drainage / rubble fill behind them. If a proper retaining wall was installed then sure half the fence cost could have been shared but the poor workmanship and material choices look dodgy.