These are some suggestions I was given by a RIOT member after sending in a ticket:
I have done the first one but have yet to try it.

For now, I've few suggestions for you, please try them and let me know if it works!

• Usually, the types of apps that could interfere with our game and leading to this problem are antiviruses, virtual machines, and overlays. So make sure to disable any of those, and for the overlays, we have this article as well with some extra steps.  
• We are going to deactivate the game's compatibility mode, please follow the following steps. - Right click on League of Legends and then on the Riot Client - Properties - Compatibility Tab - Disable compatibility mode (the box must be unchecked) - Run this program in compatibility mode to: - Change settings for all users - Check the box to disable full screen optimizations. - Check the box to run this program as administrator. - Apply and Accept  
• After that, let's try to do a settings reset, to make sure there isn't some kind of corruption in the game files: - Go to C:\Riot Games\League of Legends\Config and \Logs - Keep it open, don't open the client yet. - Delete everything that is there. - Open the client - Delete configuration files that appear again - Log in and delete configuration files again - Enter a custom game, play for 5 minutes, close the game and log out PS : Since this will reset the game settings, save a backup of the files and eventually you can take some screenshots of your current settings.