Missing Objects in Toy Box

Sometimes when I load one of my saved Toy Boxes, some items will be missing. A fountain here or a couple pieces of a hedge wall there. Usually not that many, but it's annoying and a little worrying.

It only seems to happen to the one Toy Box which is the one that connects to three others and my interior. The only differences I can think of is that it is an outdoor Box where all the others are interiors. Also, it seems to have a level name while the others do not. Perhaps because I put down a level starter tool at one point, but then deleted it.

If this is just a glitch that will be fixed in the next patch then no big deal. But I wondered if anyone else had experienced this or had any ideas as to why it might be happening.