Alt Tab causes mouse input/camera lag (GAMEPLAY)

I'm not 100% sure that this is an issue with League, but I've done quite a bit of testing and have not been able to see this issue in any other program on my computer (Including other games like DOTA and Overwatch), and I am unable to fix it within League's settings. When you load up into a game of League, everything works as expected. However if you alt tab even once, when you tab back into the game there is noticeable input lag as well as camera movement lag and general sluggishness. It's still technically playable, but I find it incredibly difficult to play even halfway decently or to just have fun with this input lag. I've checked router setting and everything like that, it all checks out. The only variable left that could be causing this issue is League itself.

1. load into a normal summoners rift game

2. check movement and camera, should be working fluidly

3. alt tab out and back into the game

4. the game movement as well as the camera should be noticeably sluggish

   Once again I am not completely sure that this is an issue with the League client, but at this point I'm about 97% sure as I cannot find anything that may be causing this issue. Interestingly enough, this does not appear to be present if you run the game in windowed mode.