The farm owner identified further issues with the tractor, including its brakes and Agricentre South attempted to fix the issue on-farm.
Five days into the trial, the brakes failed, and the tractor ran over a worker, leaving her with fractured vertebra, fractures to her arm and injuries to both legs.
The farm owner who was driving the tractor escaped unharmed.
WorkSafe's investigation found that Agricentre South had failed to ensure the tractor's repair history was communicated between staff, failed to ensure the tractor had fully operational brakes, and that wires for the warning lights were reconnected and working after repairing the brakes.
"The vehicle service industry, including the servicing of farm machinery, needs exceptional diligence to ensure the safety of the end users of vehicles and plant. Working brakes are the difference between life and death - on the road and in the workplace" Humphries said.
Agricentre South Limited was charged under sections 36(1)(a), 48(1) and (2)(c) of the Health and Safety at Work Act 2015.
It was fined $239,063. Reparations of $103,459 had already been awarded to the victim in April last year.