Yup they take the whole box and the vending machines and fridges are accessible. I also put storage places near them... Plus I tried to fire one and hire new one again but all of them did the same thing..
Are the storage places accessible? If they take the full box it means that they are going to bring that box to the storage places. If between the storage places are some walls, try to delete some of them to make a way to let the workers go directly to the storage places (sometimes doors get bugged and don't let the workers move).
If it still doesn't work, it would be great if you send us a screenshot of your game.