Alt + Tabbing while inside of Windowed Fullscreen makes little line appear (Help)

I recently factory reset the PC which seems like it affected my valorant a little bit by making it whenever I tab out, a little blue line appears at the bottom of my screen which I can only assume is my desktop background. I have no clue how to make it not be there and it also makes the game lag for a split second when I am alt tabbing (See image for the little line)