Lots of activity observed the past few days at this repeatedly 'problematic' possible nest. Male and female repeatedly entering and loitering around the hollow at dawn and dusk, but not a normal nesting changeover like other pairs. I'm starting to wonder whether this is an example of a 'bad dad' and 'bad mum' who have some kind of nest, but don't have the skills or experience to actually hatch an egg and raise a chick...???