the fencing in the first picture has large openings that some predators can get through ( mink and weasels can squeeze through a hole the size of Quarter)
use 1/2 hardware cloth over all the ventilation openings ( up high places) and close up all the lower spaces with boards or some thing else solid
also raccoons reach their whole arm though holes like that and grab s duck by the head . and pull the head through the space and eat it. it’s horrible to even think about.