When i fire my ult as draven my mouse is on the left side of the screen, but my ult flies backwards. This bug was a problem a few years ago, but i have had it occur quite a few times in my games lately.
You had hovered over Ezreal's portrait the moment where you used your ultimate, targeting Ezreal. So I don't think it's because you have your cursor on the very edge of your screen.
Not sure if this is a bug cause you have your mouse over ez portrait, Another version of this "bug" is when you have your mouse on your minimap and it fires it in the direction of where your mouse is on the minimap. They should add an option where you could turn those off.
