With some new furnitures (specifically fences are bad for this, but others do it too), when you drop them from the inventory, they skip away from the player's location and appear at a distance. This is not, in itself, problematic - you can still pick them up or move them - but when the furnitures are dropped near a level edge, they sometimes appear outside the visible area of the level. This is really annoying when you've carefully laid out a huge number of objects and then one thing goes for a jump out of the screen.
I just lost my 'christmas sign' this way - it just isn't anywhere and I'll be damned if I'm going to restore 3 hours of designing to get it.