We monitor the capacity in all parcel locker systems and will contact users to collect their parcels (and free up space) when the lockers are filling quickly. Therefore it is very unlikely that a parcel locker will reach full capacity.
As usage increases, more locker modules can be added to the current locker bank to increase capacity, you may need to talk to your building manager or body corporate to reach out to My Parcel Locker if this does become an issue.