Items Removed Warning?

I play vanilla and I have randomly (or at least seemingly) gotten this message for years.

It's not about downloading lots from the Gallery and for me it's not from mods or CC.

I can decide to play in a house I have played several times before, or a pre-made EA house and out of nowhere I get the pop-up message but I have yet to notice something actually missing. Not that I'm spending any time looking though but still. Annoying nonetheless