If we are talking here about accidental damage then the garage door and its mechanism is the *Owners Corporation’s responsibility and is covered by its building building insurance, so hand the problem to the *Strata Manager (assuming the garage door faces common property).
You would be liable for the insurance excess but the insurance should pick up the bill for the repairs to the garage door. The structural repairs are also the *Owners Corporation’s responsibility and it will have to pay for them.
The insurance might decide the garage door has been so badly maintained that it’s a maintenance issue and so refuse to pay. In that case you have no liability as it’s all the *Owners Corporation’s cost.
(* numerous confusing acronyms removed by Whale!)