Don’t forget that the Geocentric Datum of Australia was adjusted on 1 January 2017.
This is to combat the movement of the tectonic plate on which Australia sits, more than 1.5m north-east since 1994. This movement creates discrepancies between local and global coordinates that are derived from GNSS.
Make sure that you are aware of the sources of your data, including the datum, to ensure you maintain your degree of precision.
The video below from Intergovernmental Committee on Surveying and Mapping’s (ICSM) explains the datum upgrade in more detail.