Client issue, first game causes keyboard "Alt" bug

After loading a game, my keyboard goes haywire - qwer produce "warning" pings, Esc causes my computer to start scrolling through apps. It's as if my computer reads "Alt" is permanently pressed down. This bug only occurs in the first game loaded after my computer has been restarted. So, if I play a game, shut down my League client, reopen League client, the bug does not occur. If I restart my computer and then open League, start a game, or reenter a game I had to leave (because of the bug), this occurs 100% of the time.

To correct, I usually ctrl+alt+delete, then open Notepad and start typing. 90% of the time, I can then go back into the game and the keyboard works normally. The other 10%, this does not work and I must restart my computer and League client. I had this same issue about a year ago, and adapted by always starting a custom game before queuing with other players. It then went away, but has returned with the latest patch.

I have a Cooler Master Storm keyboard, up to date drivers, no special keyboard software, running Windows 10.