Grey screen after champ select

Basically, I opened champ select, than the game started, suddenly theres just a grey screen and im trying to fix it but it doesnt work. I click initiate full repair, restart my computer, and closed and reopened the game a large number of times but it didn't work. In the end It worked when I changed the video settings from borderless to full screen. Someone please fix this, because I don't want to be banned for AFK but this is what happened.