Having to buy some garbage champ off the bench just to combine 2 items and then trash the champ so you can move the item to the champion you actually want it on.
Putting an item that's part of a two-piece component only to realize you forgot the champion already had an item on it, and now you're screwed with a redemption on your vayne.
Grabbing a champion from the carousel and realizing it auto-combined with the champ you already had, thus combining their items and screwing you out of something you actually wanted.
And while we're here, I just have to ask -- why are items champion-bound anyway? What's the point? Why can't I just swap them on the fly? I'm not sure this is a problem with item combination, more than it is a problem with item permanence.
If items weren't permanent, at least I could take that redemption off my vayne and put it somewhere more appropriate.
At any rate, something here just feels bad, needs fixed.