Hi ,
If the OC is authorising and managing the works then they are responsible for the builders actions, damage and errors. How they resolve that with the builder is a matter for the contract in place with the builder (as mentioned by another commenter). If it is excluded from the building contract, it may be a cost to the OC, but it should not be a cost to you as the individual owner.
I suggest you write to the OC/strata manager to request its rectification. It should not be a cost to you or your insurer. If they refuse, then you should obtain the reasons (in writing) so that you can take it further.
Regards,
Rob T