Bird box coming away from the wall

Hi

I was hoping someone could offer me some advice. I recently moved into a new place and the previous owners fixed a bird box to the wall of the house. I was unaware of this until a family of blue tits started nesting and raising chicks. I noticed today that the bird box is moving quite a bit with the chick’s activity and it looks like it’s coming away from the wall. I’m really worried it’s going to fall down but I don’t want to interfere in case that causes the parents to abandon the nest. Can anyone advise? Will attach a photo for reference. Thanks.

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