Hi Sylvie
It’s lovely to hear you have a tenant in one of your hog houses. It is, though, not a good idea to disturb or change/add bedding to a nest which is currently in use, even if the hog is out. We may have provided the box, but it’s their home whilst they are using it. Even checking a box can cause problems, particularly if the occupant might be a female with young. They are very sensitive and can abandon or kill their babies when they are very young, if disturbed. If you want to provide extra bedding you could leave some outside so that they have the choice to use it or not.
It is quite normal for hedgehogs to return to their current nest during the night. They often make several trips out for food and nap in between. Hopefully the hog there is foraging during it’s wanderings as well as eating what you provide!
Good luck. Hope you get tenant/s in your other box/es as well.