Calculating Differences for no reason (5000 files +)

So , I was playing a custom game with a friend and I decided to leave , so I left and clicked the "x" (log-out) button. Then , it closed the client , so I launched it again , and when it started , SURPRISE "Calculating Differences" ! There is no new update (I checked with friends and still...). "Calculating Differences | Scanning files 3000 | 33% , and it goes on and on ... So please , Riot , fix this issue , because it's not the first time it happened and it usually lasts 2 HOURS+ !!! I hope I can get your attention and you will try to fix it ! Thank you.

Kindly , DawNxSilver