Unresponsive game actions

For the last few days, in every match I played, every 1-2 minutes or so there is a time frame of about 1-3 seconds in which League does not register any actions i make, and every skill I cast or movement command I issue happens after that time frame ends. In most cases, it leads me to certain death. There is nothing wrong with my ping, it remains around 40 all the time, and my fps is completely stable. I started investigating it and I figured that packet loss might be the problem, but it turns out my internet connection is perfectly fine. I can't really play like this, so does anyone have an idea on how to fix this?