Item Shop bug in ARAM?

So I'm playing a match in ARAM, I die, and I use my time spent dead to shop/sell items. Right? Standard stuff.

But I've noticed a few times now that when I'm revived, and still in the fountain, I can't undo any item purchases I've completed during my death timer. Shouldn't I be able to, as I haven't left the fountain yet? This doesn't happen every time, but I've definitely noticed it happening once in a while.

Or maybe I'm just missing something.