Now this sequence is a bit odd.
Firstly, the bird in the box is not crouching out of the way to avoid being landed upon by the incoming bird. Secondly, it looks positively hostile to the newcomer.
Nothing much has happened during the past week.
This hostility continues after the second bird has entered - these two are not a pair!
The newcomer doesn't seem to know quite what to do so it hops back onto the entrance hole . . .
. . . but it doesn't go out again. But neither does it start a fight in the box, a common occurrence when a new couple is looking for a nesting site.
Instead, it drops to the floor of the box again, and the two birds just stare at each other.
A minute later they are still there, but with their backs to each other. Clearly neither of them is looking for a fight!
Suddenly, the newcomer goes.
The remaining bird picks up some nesting material (so it must be a female) . . .
. . . and removes it . . .
. . . from the nest box!
So what was the other bird? It wasn't the fluffy one, but it clearly wasn't the female's partner!
Life returns to normal again - a conventional swap-over!
And another one! So there is nothing seriously wrong here.