Fog of war bug in new Summoner's Rift

It doesn't do this on all games, but occasionally the fog of war on the new SR bugs out mid-game and turns REALLY dark, almost black. Sometimes it has lines or zones that are less dark, colored strangely, or completely lacking the fog of war (although I still can't see enemies in it, it's just missing the shading). Makes traveling through the jungle quite difficult as I can't see any of the terrain.

I will add a (crappy) screenshot when I can.