Changing the Plan of Subdivision (that shows the car parking allocations) requires a unanimous resolution of the OC (at least in Victoria, probably similar in other states).
Unless that was done the re-allocation was illegal. I suspect the EC and the manager know this.
You cannot just register the change. The Titles Office will want to see proof that the OC legally agreed to to it.
Get your Plan of Subdivision, confirm your space and then request from the manager a copy of OC resolution that voted to change it. It it wasn’t voted for legally then they are bluffing you.