The 06z version of osmi still picks the anomaly up
https://tools.geofabrik.de/osmi/?view=areas&lon=147.65078&lat=-42.86792&zoom=16
The small water feature near the intersection of Carlton River Road and Provence Drive is an inner but the outer wooded area that surrounds it is not in the relation so you need to either delete this water from the existing mp or add the wooded area surrounding the water to the mp.