[GAMEPLAY] SOMEONE HELP MEHH PLEASE

So... About a week ago, I found it happened. During the preseason, I decided to level up my low level account. And some of my friend wanted to play with me, so I went on to my main account. And I found my character is flashing around. As in like... teleporting a short distance. So I thought its my internet's problem. But my brothers are not lagging. So I logged in with my brother's account and played, it was fine. So I re-downloaded league of legends, and it still happens.