I faced this issue a few days ago and it has only ever happened to me once. My mouse is a piece of crap and sometimes when I try to single click, it will double click. When I was asked to discard a card I selected one but my double click thingy kicked in and I accidentally discarded a second card at the same time. Sucked cause it was one of that decks few upped cards. But yeah... the delay between clicks when it happens to me is reallly short, probably could be measured in 10ths of a second, if that helps.
