Building managers will generally do as they are instructed by the Owners Corproation and it’s the OC with whom you have the dispute. In a case like this, it’s often a case that the committee members don’t want to have to pay fees that would be increased by getting the work done, however the OC has a legal duty to maintain and repair common property.
It sounds like you are going to have to take the OC to VCAT, seeking orders to force them to fulfill their legal duties. Have a look at this information page then consider getting together with any other owners in your block who are suffering the same problem to hire an experienced strata lawyer to conduct the case for you.
Good luck.