Whilst checking the nest boxes today, phone substantial damage to two of them, whereby the entrance hole has been vastly increased by something.
We blame the woodpeckers, but haven't ever seen them doing it. Cleaned them out in late summer, and there positions are such that they are not visible on my daily walk through the wood so it was a bit of a surprise. Was able to carry out some simple repairs, so hopefully now usable. One other box had a little damage, which looked quite recent, so I'll try and keep a closer watch on it.