Items Removed Warning?

Maybe it's removing things attached to other things? Emitters that left bits attached to your Sim, random objects left in spots they shouldn't be, bits of files related to CC, objects that were tied to a Sim's action in a downloaded house that shouldn't be there anymore (water in the tub, steam from the shower, a book being read, etc.)

I know in Sims 2 objects, actions, and memories could become attached to houses. Then if you moved them, uploaded or downloaded them, those bits went with it and wreaked havoc wherever they got added. It was best to use SimPe and clean installer to make sure any houses were truly "clean" before moving or sharing.