I’ve heard of worse – like tradies who fill their garages with their gear and leave notes on the windscreens of legitimate visitors, threatening terrible consequences if they park in THEIR visitor space again.
Write to the committee asking them what their plan is in terms of Notices to Comply and orders at NCAT.
Notices on doors and cars are just an irritation, NTCs and Orders carry the prospects of fines which, because they are paid back to the Owners Corp are worth pursuing.
If the SC say they’re doing nothing or just don’t respond within two months, you can start pursuing them under Section 232(2).