This just started happening to me today. Its weird because nothing changed. The same save file I have been playing in for years. I have never used mods. I didn't buy a new pack. I've played since the last update. No reason for it to start randomly today. I am on PC.
My current household uses the sale tables to make money, and I can't move item into the table inventory meaning she can't sell stuff. It also does it with fridges, and sticker storage boxes, that I have tried so far.
ESC works to drop the item from the cursor and puts it back in the original inventory, but that doesn't help with the sales table inventory or items that go bad like milk and eggs.
If you select the option to open up the screen that shows multiple items and select one item at a time and put them into the world first. You can then put them into the Sim's inventory. This is a tedious work around, but it does work. ESC can allow you to select one stack and put it into the Sim's inventory, but you have to hit ESC right after you drop it in. It is all about timing. The easiest way is to select items and put them into the world first, one at a time.
