You should be able to find out this information from the strata records. Your Strata Manager should have all of these records.
As an owner you are able to access these records for a small fee. Contact your Strata Manager and advise them that you wish to search the records and organise a date and time to do this.
To save yourself a lot of time try and narrow your search down to a specific period in time so that the Strata Manager will have the material ready for you.
If, after searching the records, you believe that an error has occurred in the making of the original decision to grant exclusive use of this area then either you, or the owners corporation may want to take this matter to mediation and then possibly on to adjudication.
You would no doubt be aware that the owner with the exclusive use grant will fight hard to retain it and will not give it up easily. Put yourself in their ‘shoes’ and you will understand that they have a lot to lose.
This is a complicated case so you may need legal advice.
Incidentally, I can’t understand why the owner’s corporation paid for the repair of the membrane when it was the lot owner who caused the damage??? An owner cannot damage common property and usually cannot drive a nail or a screw into common property. The lot owner should have been made to pay to repair the damage to the membrane.