Varus Q not firing upon release (smart cast)

Each game I play with Varus this happens at least once or twice. With smartcast, when the player releases Q to fire Piercing Arrow, occasionally the arrow will continue to charge until a second press. This is definitely not intended as releasing Q fires the arrow 90% of the time. This has been really bothering Varus players for years. Please fix this Riot, thanks :)!

I've linked a video of the bug from another player.