MACBOOK PRO RETNA

There has been a bug on my macbook pro retina for the past few month. I can't remember which patch mea culpa. It's hard to explain, but the image is very self explanatory (https://imgur.com/a/1Bma7). There's a window of the game that pops in the background when I play. This happens with every resolution, and definitely causes FPS problems since it layers 2 game windows. Wondering if anybody else encountered this problem and if someone knows how to fix it.