Weird Light Square

Right, so I’m having this odd issue with this big ol square of light following the camera/player around in the world and drastically changing how things look.

http://i.imgur.com/I1Zo0r5.png (The forums, as always, won’t let me embed anything).

And here are two videos of it in action:

https://puu.sh/wZidC/8a8fc78ad5.gif
http://puu.sh/wZlz7/e8db77a921.gif

I’ve been through every single setting in the directional light and skylight, but there’s nothing in either of those that affect this square of light whatsoever.
I’d really appreciate some help on this as it’s wrecking my scene as the player walks, and this isn’t the only project I have where this issue occurs, either.

Edit: Am dumb, and the culprit was the LPV fade range in my post process volume.