Borderless mode is broken

So, while in borderless mode, the FPS cap will auto set itself to 60, even if the cap isn't on. That's not the bad part.

The bad part... occasionally, the FPS cap breaks and goes to 30, and the game hardcore stutters the entire time it's at 30 FPS. If I keep moving around (I think it has something to do with certain things being on screen) it'll eventually go away, but as soon as I move back to where I was stuttering, it happens again. If I alt-tab out of League and then click back in, the stuttering goes away for a few seconds.