Screen freezes/FPS drops

For the past few weeks, my screen has been freezing randomly in-game. When it comes back the fps counter shows that I dropped around 60 frames (from 144), but, as I said, it just freezes on a single frame. It lasts from .5 seconds to 2 seconds. It is extremely annoying.

Things I have tried: Full repair Computer restart Turning the graphics all the way down Changed Nvidia settings to performance Closed everything else unnecessary while playing

One thing I have noticed is that the champ I'm playing sometimes jitters around as well as minions when I come back from the freeze. Maybe this has something to do with my ping? I do have unusually high ping in League, 114 consistently, and only in League.

It also seems to happen often when an ability is used. Maybe that's just coincidence, but it's something I've noticed.

Is there anything else I can try or am I just going to have to bear this?