It also happens when you delete an object in the object list (with the suppr key also) as long as there is still one object in that list. Like if the object is deleted, focus goes to root folder and try to delete again.
And the tooltip seems to go down on each item deleted.
(Three objects in the list, I delete the last one, the tooltip indicates sound folder, I delete the second one in a row, the tool tip indicates a place under the 'music' folder)
The tooltip doesn't really go down, I guess in fact the list of remaining objects go up.