I'm wondering if this is the same female with a deformed beak from sighting #4439813 (30.7.22). In that sighting, @ChrisDavey noted that the beak tip could snap off? If it's the same bird, then I think the curved tip may have broken off. She did not close her beak at all while I was observing, and tried to chew part of the hollow without success. I did not sight the male, but there was loud and audible, echoey scraping and scratching from within the hollow, which I assume was the male. This is a problematic tree if they choose to nest - home to six Kreffts gliders (I am reliably informed) and a bee colony.
Lisa, I think you are correct. The upper mandible could well have broken off and then reshaped with working the hollow. To me there are some white edgings to the breast feathers which look similar in one of your images to the one posted at https://canberra.naturemapr.org/species/15862