The owners corporation is responsible for all common property. In the absence of the special resolution by-law that they should have extracted from the renovator, then they, or their successors, have to wear the consequences.
This is why I have been saying for the past 15 year that there are serious problems with letting owners do what they want with common property on a nod and a wink.
It’s also why a common property by-law requires someone to be given responsibility for the ongoing maintenance (with that defaulting to the owners corp if they are stupid enough not to insist that responsibility shift to the renovator).
So look no further – if the Owners Corp can’t come up with a record of a registered by-law saying the previous owner has taken responsibility for the upkeep of the balcony, then it’s still their responsibility and they are obliged to fix it.
You can take that to the bank … and NCAT.