As much as I loathe the “this is an issue between two residents” excuse for the owners corp not getting involved, I suspect this is one of those rare cases where that’s valid.
It seems like common property is not involved and it’s hard to divine what by-law has been breached.
That’s not to to say you don’t have a case, just that the owners corp doesn’t really have a dog in this fight.
The positive aspect from your point of view is that it has previously been established in a NSW court that the landlord has a responsibility for the behaviour of their tenants.
Record the door slamming, then present Fair Trading and NCAT (if it ever gets that far) with the evidence.