As shown, overlooking the view zooms to a minimum, you can see the entire grid, creating a light volume, after amplification beyond this grid, will disappear, which is what the problem is. In udk when there is this problem.
Closing since this is a duplicate post: https://forums.unrealengine.com/showthread.php?49386-About-the-size-of-the-volume-box-disappears-world-problems