Patching the game

Ever since late season 5, I have had on and off issue with patching league of legends. Some days it takes fucking hours, with it "scanning files" whilst on 33 percent. Other days it takes less than 6 minutes. Why does this happen and why is it not constant. This doesn't happen from patch to patch, I have had this issue occur to me on the same patch because some times I couldn't take waiting and would just close league all together and open it again and all of a sudden it would patch rather fast and other times I'm just forced to wait. Please help.

(Edit) Today I was patching league and it got to about 21k files scanned which took about 2 hours to accomplish before I decided to close the program and start the process over again, I am currently at 2.2k files scanned and its been approximately 10 minutes.