In NSW your conveyancer should have asked the OC for. Sect 184 certificate. It’s the only official statement of what’s owing on a lot.
If the Sect 184 shows no money owing, then it’s the OC problem. They can’t collect any money from you because they made the mistake.
If you are relying on strata search or the vendor for a report on any arrears, then that’s your problem and the OC is entitled to their money.
I have personally had a situation where my solicitor got it wrong. Fortunately for me I was able to rectify the mistake.