It would seem to me that if you have a case it's against against the builder not the management company, perhaps under the homebond system. Any problem we've had with the structure of the apartment we've had to go back to the builder with. Still I've never heard of insurance paying for work missed to fix a fault though.
As for immersions, they're temperamental things, sounds like you were unlucky with yours but it's certainly not a management company thing, no harm to check it out with the builder anyway.