[Client} 33% Error

This error appears to happen randomly, as I have no idea how to reproduce it because it happens out of nowhere and is only able to be noticed when opening up the League client. At the top it will say there is 33% finished in calculating and scanning files. It will continue scanning files for an unknown amount of time. So far I have had this happen around 6 times to me. Riot, please find a way to fix this bug/error/glitch