LoL window becomes inactive during gameplay, causing inability to move or use abilities.

Since last patch, the window that LoL runs in will randomly become unable to interact with until I alt-tab back in, and left click once back in. There seems to be nothing that triggers it. I could sit idle somewhere on the map not pressing anything and have this happen as soon as I choose to move, or I could pop ghostblade and have it happen during the middle of a team-fight. Resolution conflict seems to be null, as it happens in every resolution and whether it's fullscreen, windowed or borderless. I have uninstalled/reinstalled, repaired, killed every process not needed for LoL to operate. I am completely stumped by this, as it has never happened prior to the previous patch.