Twitching cursor

When I enter the rift (as soon as the game starts) my cursor seems to teleport, for example, when you try to click on the 'BUY' button it will either go backward or go further than the buy button. This glitch only happens when I enter the rift, nowhere else. When I try to input my abilities it twitches and usually misses the champion. Please fix! I know this is not a problem with my mouse but instead with the game.

Thanks for reading.