The bug occured while in my first placement match's Champion Select. I was assigned Jungler (queued as Fill) and the client hanged for a 2 seconds when I hovered Master Yi in ban phrase. Then, after hitting Ban, everything went on fine, except the UI of the client completely blocked as if it had crashed, but all the sound in the background were playing correctly and I knew exactly when I force dodged the draft by the bug. Ending one of the processes of the client using Task Manager fixed the problem for the time being.
Note: Changing the monitor's resolution causes the client to not be able to show correctly, but still runs in the background. The same happened when I tried to close and re-open the client after the bug occured and before I ended the process in Task Manager.