This isn't too major, but whenever I leave a current game and rejoin, be it with a co-op partner or not, sometimes my furniture will turn into a box again and launch all of my stuff inside of it. Usually this happens to a rolling desk but it's happened to my cabinets too.
Co-op or single player, any map. Buy furniture and a few items of any type. Put all the furniture close together (or apart) against the wall and put the items in. Then leave and save the game, and then rejoin it. Something should turn into a box again and launch a few items.
Quest 2.