Short FPS drop every game at around 7 minutes

From 8.13, I started having huge FPS drop every single game, during approximately 40 seconds. The vast majority of the time it's around 7 minutes into the game, then it goes back to normal.

It happens on every mode, every map.

By huge FPS drop I mean, I will have from 5 to 10 FPS during 40 seconds. I thought maybe it would stop with 8.14 but it's still there and I pretty much can't play ranked until it's fixed.

I'm on a MAC, here are the specs: http://prntscr.com/k80stx It's in french but you should not have trouble understanding.