My computer is a 2014 15' MacBook Pro Retina on 10.9.5. I've had this happen in every Ren'Py game I have, across all publishers, but non-Ren'Py games don't have this particular issue. If you start windowed and then toggle full-screen it's fine (until you quit and launch in fullscreen mode). Note: it only happens if you start the game in fullscreen mode. I get it on every Ren'Py game I've tried.
