Left click ability cast bug

Hi, Ive been having this problem where I have to click multiple times in order for left click to work. This usually happens when I cast abilities. Its really annoying and affects the gameplay. And while smartcast fixes the problem, it still requires 5-6 clicks to open the shop. I've tried searching in google for hours and all the answers are either "get a new mouse"(this only happens inside lol, already tried 3 mouses) or "delete input.ini.file" which only turns the keys to default(never made any changes). Is there anyway someone can help me fix this? Ive asked this before but nobody answered. Im using windows 8.1 if that makes any difference