What is it about the league client...

.. that makes it act like such a piece of shit? These things ONLY happen when I'm playing League. I took a long break from this game and played a lot of other shit and never had any issue even remotely close to this.

But whenever I play League, like just now, I would press ONLY SHIFT on my keyboard and it'd start randomly spamming my last copied Youtube link. Or it'll hardlock a random key on my keyboard and spam it non-stop. Or it'll act like some other function key or something is pressed and start opening up random Windows apps/windows when I'm trying to press buttons in-game.