In a component with a slot containing multiple items, changes to the items stop propagating in the instance once any individual item within that instance has been manually overridden.
Consider a menu component containing a slot with menu-item components. At some point, I use that menu component by instantiating it inside another component — say, a menu-app — which then appears across multiple views. I want any changes made to the menu-items to propagate to all those instances, keeping every view consistent. And this works as expected, until I make any change to any of the menu-items within the instance. I could understand that manually overriding a specific item in a slot prevents changes from propagating to that same item — I could live with that. But the problem goes further: changing anything on any item — such as its position in the stack (which is critical if I ever decide to reorder the menu items) — completely breaks propagation of any slot-level changes across the board.