Mouse not connecting/slow to connect to game

The mouse will not register most of my clicks or it will be very slow to respond. The FPS in-game is fine, and other champions (my team and enemy) seem to be able to click easily. (My partner has had the same clicking issue)

There's no ways to reproduce the issue, some games it's just fine, while in others it will be slow in responding with every click. It seems that the issue gets worse for me near and after the 20 minute point in game, and it can work perfectly fine before that.

The clicking is an issue for anything, targetting, movement, store selection/purchasing/undo-ing/etc, flash directions, anything that requires the mouse.